Square-Cube Law and fantasy physics

[MoiMagnus]

Generally if you want to "solve" the Square-Cube Law, you have to make big things either lighter or stronger. The cube example above is pretty trivial, and you'll have a hard time justifying why 8 cubes somehow weighs less than 8 times as much as a single cube.

Let me present you "Object-Oriented Physics":

In D&D and many other games with magic, teleportation spells consider a "creature with its equipment" as a single entity, and some other spells might refer to "objects" as entities too. Concerns over corner cases are often dismissed as "this is magic", but the alternative is to assume that the notion of "object" is actually a physical notion.

With OOP, things that are linked together to form a single object have special properties:

1. They are recognised by magic as a single entity
2. Their weight is not proportional to their volume and density, and instead have a ^(2/3) exponent. In other words, big objects are lighter than the sum of their parts. Linking two objects or mass A and B together give an object of mass (A^(3/2) + B^(3/2))^(2/3).

As a consequence of OOP, there is no longer and issue with the square-cube law, as the mass now increases with an exponent 2/3*3 = 2, hence it is a square-square law which works.

(Note: Try not to look to hard at the other consequences of getting rid of the square-cube law. For example, you might need a fair share of "magic" to make microbiology and astronomy work anywhere near what we know IRL.)

[Lord Torath]

Here's how I run it.

Weight and mass of giants follows the square-cube law. Twice as tall, eight times as heavy.
Weapons also follow the square-cube law.

Armor and clothing follow the square square law. Twice as tall, four times as heavy.

As for what can a giant carry? Handwave it as they can carry whatever gear you (the DM) decide they can.

Are your players playing giants as PCs? I use this (half-giants are 12 feet tall, so are size L)
Encumbrance: Small-sized characters multiply their Weight Allowance and Max. Press by 0.75. Large-sized characters multiply their Weight Allowance and Max Press by 2. Huge size multiply by 4, and Giant-Sized by 8.

I think that might have been a 3.X thing? It's mostly a handwave, but I saw it and thought it fit. Feel free to adjust the multiplier until it fits for your particular size of giant. Again, this affect encumbrance only and not damage (although most giant weapons in 2E did double or triple damage before adding the strength bonus. I think storm giants - 25' tall - might have done quadruple damage).

As far as giants lifting each other, maybe they can't. Thri-kreen in (2E AD&D) Dark Sun weigh 450 lbs, and generally can max press a good bit less than that, so they cannot do a pull-up. If you don't want to have giants giving each other piggy-back rides, just say so.

[Devils_Advocate]

3.5e weights range from 500 kg for Hill Giants to 5500 kg for Storm Giants.

Hmm. Let's actually crunch some numbers here.

In 3.5E, a storm giant has a Strength score of 39. Anything under 1,864 lbs is a light load for a Medium creature with that Strength. But the storm giant is Huge, so we need to multiply that number by 4 to get 7,456 lbs. That's roughly 62% of their stated weight. It looks like an average human character is 157 lbs. 62% of that is 97 lbs. Which means that a storm giant can carry the same percentage of their own body weight as... a human with 17 or 18 Strength.

That's like the top percentile of the general population. Even if we assume that the stat block is only for the elite warriors of their kind, it seems safe to conclude that storm giants are at least as strong relative to their size as humans.

How about in 5th Edition? Well, now a storm giant "only" has Str 29. That would give a Medium creature a carrying capacity of 435 lbs. But again, the storm giant is Huge, so we quadruple that for a total of 1,740 lbs. I'm not sure that their weight is even listed anywhere, so let's go with 3.5's approximate 12,000 lbs. They can carry 14.5% of that now. The average human is 165 lbs. 14.5% of that is just about 24 lbs... which is less than the carrying capacity of a Str 2 human. Yikes, that's a pretty big difference!

Oh, wait, they do have a listed height, so let's see. Divide 26' by average human height, and... they should be very nearly 100 times human weight, if of the same basic shape and density as humans. Which means... they're even heavier! Oh dear.

So looks like storm giants got squarecubed between editions. If typical Strength scores in 3.5 roughly doubled each size category along with carrying capacity for a given Strength, and carrying capacity grew exponentially with Strength... Wait, let me see if I can work this out.

1. Increasing each of a creature's 3 dimensions by a factor of 2 increases its weight by a factor of 8, provided it maintains the same density.
2. Increasing each of a creature's 3 dimensions by a factor of 2 also increases its carrying capacity by only a factor of 2, provided that its Strength remains constant.
3. But! Assume that increasing each of a creature's 3 dimensions by a factor of 2 also increases its Strength by a factor of 2.
4. Increasing a creature's Strength by 10 increases its carrying capacity by a factor of 4.

So generalizing,... increasing a creature's dimensions by a factor of N increases its weight by a factor of N^3 and carrying capacity by a factor of N, with constant Strength. But if its original Strength S also increases by a factor of N... How much does that increase the number of tens in it? Well, by the difference between the new and old Strength divided by 10. So N times the original Strength minus the original Strength, divided by 10. So (NS-S)/10, or (N-1)S/10. So carrying capacity increases due to Strength by a factor of... 4*(N-1)S/10. And also by N so... by 4*N(N-1)S/10. So the ratio of carrying capacity to weight goes up by a factor of... [4*N(N-1)S/10]/N^3, or... [4*N(N-1)S]/[10*N^3]?

... I don't even know what to do at this point. Can someone check my math?

[Jay R]

Or possibly,
Player: How much does the giant's sword weigh?
DM: Probably less than all the gold pieces currently in your backpack. Do you really want to start tracking weight?
[emphasis added.]

It's strange how many people just assume that everyone has the same values as them. "Pshaw, inventory tracking, am I right? Who would ever want to do that?"

I didn't make that assumption. I explicitly modified that argument with the adverb "possibly". That argument works in some games and not in others.

[And by the way, I'm the one in our current D&D group that does track inventory.]

It's strange how many people just claim others assumed things that they did not.

[PhoenixPhyre]

The rules are not scale invariant. Specifically, the rules (especially 5e's carrying capacity ones) are designed for two cases
* PCs, who are uniformly either Small or Medium, with the former explicitly not affecting carrying capacity.
* their mounts and beasts of burden, who are Large and/or have special rules about how they interact with such things.

They are not a generalized "physics of the world" statement. And any attempt to use them as such will produce absurdities by design, because you're applying a rule outside its region of applicability. Like trying to sum the series x^n outside 0 < x < 1. Those absurdities are not the rules' fault or even any meaningful statement about the world being represented. Merely "dude, that pitchfork is not a soup spoon."

------------

On a more general note, real world physics is not scale invariant in any dimension(*). Not as variant as the 5e rules, but still quite variable. For example, the assumption that a giant is just a scaled up human doesn't work even when looking at comparable real-world creatures. Guppies and megaladon-size sharks differ substantially in layout and how much of their mass is used for various things. Because among other things, organs don't scale linearly. Same when comparing small quadrupeds and elephants.

(*) mass, length, time, charge/current. Extremes of any one of these cause a change in the fundamental laws that apply (mass scales, for instance, go from a regime where quantum mechanics is dominant and the notion of "particles" as discrete objects with well-defined positions and momenta is silly to the classical limit, where things behave like we normally expect, all the way up to the GR limit, where mass and energy are basically the same thing and all sorts of fun stuff happens).

[KorvinStarmast]

DnD nor any fiction doesn't need to "solve" any question of physics with anything. Because the square cube law isn't a thing that just exists and can be forced onto the universe to suddenly make a dragon be crushed under itself. You don't have some weird metaphysical power to point at a giant and say "you don't exist because square cube law". thats not how science works. thats not the process of figuring out how the world functions.

the process is: "oh look I see dragons fly around and giants move just fine in this world" and compare it to a world where square cube law exists, where they wouldn't. Therefore they are a world where square-cube law doesn't apply and no scholar/scientist/wizard/whatever within that world would even come to the conclusion such a law even exists in that world. {snip the rest}

+ eleventy three.

In the introduction to the game I'm currently running, I included the following:
Answering these kinds of questions doesn't improve the game, and might hurt it. Therefore the best way to handle such a question is not to ask it in the first place.

My world building includes the bones of dragons being made of something different from other bones (think the difference between steel and titanium, for example, in terms of strength to weight) and they aren't fat, they are lean. Also, great post thank you!

Dinosaurs absolutely DO NOT violate the square-cube law... Neither do giant arthropods from the past.

But in any case, my personal take is that in worlds with magic, aether is a real thing.
And creatures exist simultaneously in the physical world and in a world filled with aether. The reason giants and dragons can exist is the same reason blue whales don't have their organs crushed by their own weight. Buoyancy... Except instead of water, it's aether that (partially) sustains the weight of giant creatures and objects, making them easier to lift, move and carry than they would be in the real world.

I am sooo stealing this.

Let me present you "Object-Oriented Physics":

Loved your post, my brother has been doing data base stuff for decades, and he tried to explain OOP to me some years ago. Your post helped, thank you!

On a more general note, real world physics is not scale invariant in any dimension(*). Not as variant as the 5e rules, but still quite variable. For example, the assumption that a giant is just a scaled up human doesn't work even when looking at comparable real-world creatures. Guppies and megaladon-size sharks differ substantially in layout and how much of their mass is used for various things. Because among other things, organs don't scale linearly. Same when comparing small quadrupeds and elephants.

There's a lot of sushi in a megladon, right? Hungry hippo wants to know!

[Duff]

The simplest explanation is to say "Density is not a meaningful concept in this world" Things don't sink or float because of how much space they take and how much they weigh. They sink or float based on "Floatyness" - and attribute which is based on the elements they contain, and on their type and nature.
Any other interactions which would be based on density, are also based on other properties.

Strength is not based on muscle cross-section. Musculature is a physical manifestation of strength

Then, "A giant that's twice as tall as a human, is twice as strong, weighs twice as much and is the same density as a human when you push, punch or cut them" makes perfect sense

[Mechalich]

There's a lot of sushi in a megladon, right? Hungry hippo wants to know!

Actually, there's no sushi in a megalodon. Sharks retain high concentrations of urea in their body tissues (for both metabolic reasons and buoyancy) and as a result shark flesh smells strongly of ammonia which needs to be masked by cooking/spice/etc. in order to be palatable.

[Greywander]

I think a lot of people are still missing the point. I'm still seeing a lot of "just don't worry about it" or "it's fantasy it doesn't need to be like real world physics" or "here's a lore justification for why this works," etc.

If it has a Strength score, and a listed size, then it has a defined carrying capacity. What isn't defined is (a) the weight of the creature, and (b) the weight of their equipment. I can "not worry about it" up until one of the players attempts to pick up a giant, or loot the giant's gear, and then I need to assign a weight to these things. And if it ends up, as one other user so poetically put it, that the giant can't lift their own pants, it's an instant break in immersion for everyone. But it's also equally immersion breaking if it turns out those pants are lighter than air (though in fairness, maybe fantasy physics makes this not matter, i.e. the pants won't float).

So the real issue is needing to assign a real, tangible weight value to an item (or creature), and how that weight value might interact with a giant-sized creature's carrying capacity. I'm not looking for a justification for why the giant doesn't collapse under his own weight, I'm trying to figure out how to avoid a situation where the giant can't lift his own pants.

As an aside, I think it could make for a neat premise for a sci-fi story involving giant robots to have a meta-material that ignores the Square-Cube Law and behaves the same at any scale. This probably means that material isn't great for building small things, since traditional materials would be stronger at that scale, but would work well for really big things like giant robots. Not sure what kind of mechanism the material would use in order to achieve that property, though, and that would likely be an important part of the setting or plot.

[Mechalich]

If it has a Strength score, and a listed size, then it has a defined carrying capacity. What isn't defined is (a) the weight of the creature, and (b) the weight of their equipment. I can "not worry about it" up until one of the players attempts to pick up a giant, or loot the giant's gear, and then I need to assign a weight to these things. And if it ends up, as one other user so poetically put it, that the giant can't lift their own pants, it's an instant break in immersion for everyone. But it's also equally immersion breaking if it turns out those pants are lighter than air (though in fairness, maybe fantasy physics makes this not matter, i.e. the pants won't float).

So the real issue is needing to assign a real, tangible weight value to an item (or creature), and how that weight value might interact with a giant-sized creature's carrying capacity. I'm not looking for a justification for why the giant doesn't collapse under his own weight, I'm trying to figure out how to avoid a situation where the giant can't lift his own pants.

The square-cube law influences how animal physiology operates, but only imposes hard limits at the very upper end, one that no land mammal, or any D&D giant is approaching. Sauropods were much larger. Maximum mammal size seems to have been restricted by other factors, such as lung capacity and reproductive issues. That said, land mammals such as Paraceratherium reached heights equal to that of any D&D giant. The scaling problem for something like giants is how to take some that appears to be isometric and claim that it's actually allometric as real animals are and a giant would need to be to exist. The easy answer doesn't involve any magic, but simply relies of having something like a giant be drastically different 'under the hood' from a human being while having superficial correspondence (though some giant art is more reasonable than others, giving them broader legs and waists than a simply up-scaled human).

Note that most large mammals in the same rough weight class as various giants (giants have weights given in 2e and 3e materials you might as well just use them in 5e) are quite strong for their size and if this is extrapolated onto giants - which is not unreasonable aside from balance issues associated with bipedal locomotion - giants would have no trouble handling their equipment. And most giant gear isn't being 'cubed' in any way compared to human-sized equivalents, because it's generally expanding only in two dimensions to get longer or broader, not necessarily any thicker. Animals like elephants and bears, when handling objects they are able to grip, make this abundantly clear.

[theNater]

So the real issue is needing to assign a real, tangible weight value to an item (or creature), and how that weight value might interact with a giant-sized creature's carrying capacity. I'm not looking for a justification for why the giant doesn't collapse under his own weight, I'm trying to figure out how to avoid a situation where the giant can't lift his own pants.

Okay, with weight and carrying capacity being the key issues, let's use those as first principles. We can be vague about size or, if it becomes necessary, fill it in to fit. First we need a baseline of how carrying capacity and gear weight relate. I'll use some values for Medium-sized characters from the D&D 5e PHB because it's what I have handy.

Item	Percentage of Carrying Capacity
Body Weight	90-110
Clothing	1-5
Little Weapons(daggers, rapiers, handaxes)	0-3
Mid-size Weapons(quarterstaves, halberds, greatswords)	2-6
Big Weapons(mauls, greatclubs, pikes)	4-15
Light Armor	4-10
Medium Armor	8-20
Heavy Armor	25-50

Now we can use this to estimate the weight of the giant's gear based on their carrying capacity. A giant with carrying capacity of 1000 lbs. can be expected to wear clothing weighing in the neighborhood of 10 to 50 lbs., with their pants probably not being more than half of it. Now we've got a range around which we can make a specification that makes sense to your group; you can say the pants are around 15ish lbs. and adjust up or down if that seems weird to you or your players.

Note that we haven't found the size of the pants, and may never need to. But if we do, we can do a similar estimate with sizes as first principles, and whether the result adheres to the square-cube law or not is irrelevant. As long as all players are comfortable that the weight seems reasonable and the size seems reasonable, we don't need the weight and size to correspond in any meaningful way. We're aiming for verisimilitude, not realism.

[Satinavian]

Would having a different value for gravity in the fantasy world (or the planes of different beings' origins) open up the range of options for body types?

Generally, when one has normal and fantastical elements in a fantasy world and the fantastical elements seem to have problem with real world physics, the last thing i would attempt is trying to change the physics of the fantasy world to allow the fantasy elements. Because as a result you can basically be certain that now all the normal stuff doesn't work anymore.

[KorvinStarmast]

It's strange how many people just claim others assumed things that they did not.

Standard internet, ain't it?

Actually, there's no sushi in a megalodon. Sharks retain high concentrations of urea in their body tissues (for both metabolic reasons and buoyancy) and as a result shark flesh smells strongly of ammonia which needs to be masked by cooking/spice/etc. in order to be palatable.

Fair enough, but when I caught some black fin sharks (man, almost two decades ago!) we ended up with steaks on the grill. Better than swordfish (and I love me some swordfish).
IIRC, I may have soaked them in milk for most of the day before I grilled them, but maybe not. A little salt and pepper, on the grill, palatable and more! Yummy. Mind you, these sharks were around 3 feet long (the boat was only allowed on Really Big One, and someone else caught that; it was longer than I am tall), so the ones I got were hardly "a megalodon" in terms of meat harvesting.

[Alcore]

However, it does still leave the problem of a creature not being able to lift another member of its own species. But is that a bug, or is it perhaps a feature?

it is a feature (in that it conforms to physics)

... but an accidental one in my opinion.


See an ant could lift several other ants but an elephant? It was quoted to me that it can only lift 10% extra of its weight. You will find a similar trend with other animals; the bigger they get the less likely they are of being able to run off with another member of its species on its back.

[NichG]

I think a lot of people are still missing the point. I'm still seeing a lot of "just don't worry about it" or "it's fantasy it doesn't need to be like real world physics" or "here's a lore justification for why this works," etc.

If it has a Strength score, and a listed size, then it has a defined carrying capacity. What isn't defined is (a) the weight of the creature, and (b) the weight of their equipment. I can "not worry about it" up until one of the players attempts to pick up a giant, or loot the giant's gear, and then I need to assign a weight to these things. And if it ends up, as one other user so poetically put it, that the giant can't lift their own pants, it's an instant break in immersion for everyone. But it's also equally immersion breaking if it turns out those pants are lighter than air (though in fairness, maybe fantasy physics makes this not matter, i.e. the pants won't float).

So the real issue is needing to assign a real, tangible weight value to an item (or creature), and how that weight value might interact with a giant-sized creature's carrying capacity. I'm not looking for a justification for why the giant doesn't collapse under his own weight, I'm trying to figure out how to avoid a situation where the giant can't lift his own pants.

As an aside, I think it could make for a neat premise for a sci-fi story involving giant robots to have a meta-material that ignores the Square-Cube Law and behaves the same at any scale. This probably means that material isn't great for building small things, since traditional materials would be stronger at that scale, but would work well for really big things like giant robots. Not sure what kind of mechanism the material would use in order to achieve that property, though, and that would likely be an important part of the setting or plot.

But you're never going to have this problem since carrying capacity scales exponentially with size (at least both in 3ed and 5ed). So I don't get the problem if this isn't a lore issue. The system already guarantees that giants can lift their pants.

[kieza]

Although it never actually came up in my games, my mental justification has been that every really big creature has to be somehow magical. Extraplanar creatures draw a little bit of magic from their native plane to enable them to exist in the material plane's physics. Big creatures from the material plane, like dragons, have to get that magic from elsewhere--from their diet, or by becoming spellcasters who can use their magic to support themselves.

I actually wrote this into the biology of my dragons: when they're hatchlings, they can get along just fine with pure muscle power. As they get older and bigger, they have to start using magic in order to fly. Eventually, they get so big that they have to start using magic just to walk around without their femurs snapping--and if they live for a really, really long time, it gets to the point that they can only fly or do heavy physical activity for short periods before they have to regain their strength. The very oldest of dragons even have to undergo torpor--a period of dormancy during which they build up their magic reserves for increasingly rare periods of activity.

Dragon eggs are abandoned by their parents--they leave clutches of eggs in suitable, secluded nesting sites, but the hatchlings are left to fend for themselves. While there is a lot of variation in mindset among young dragons, the roar-smash-burn variety tend to die young. The only dragons that live to old age are the ones that invest, early on, in hoards of magic that they can tap, enchanted lairs, and so on: all the others get killed, either when they get too old to fight off younger rivals with more endurance, or when a dragonslayer catches them at their weakest.

[OldTrees1]

So the real issue is needing to assign a real, tangible weight value to an item (or creature), and how that weight value might interact with a giant-sized creature's carrying capacity. I'm not looking for a justification for why the giant doesn't collapse under his own weight, I'm trying to figure out how to avoid a situation where the giant can't lift his own pants.

At first you would assume pants would scale as linear increase^2, however they probably need to become a bit thicker to accommodate additional strain, but not all the way to being proportionally thicker. Consider if pants increased in mass as linear increase^2.5, then larger creatures would still lift their pants, but would wear shorter pants.

The same would be true about armor and about most items.

This results in larger creatures having larger but proportionally smaller items.

[KorvinStarmast]

Although it never actually came up in my games, my mental justification has been that every really big creature has to be somehow magical.

Makes sense, since they exist only in fairy tales/faerie stories.

[Lord Raziere]

Although it never actually came up in my games, my mental justification has been that every really big creature has to be somehow magical. Extraplanar creatures draw a little bit of magic from their native plane to enable them to exist in the material plane's physics. Big creatures from the material plane, like dragons, have to get that magic from elsewhere--from their diet, or by becoming spellcasters who can use their magic to support themselves.

I actually wrote this into the biology of my dragons: when they're hatchlings, they can get along just fine with pure muscle power. As they get older and bigger, they have to start using magic in order to fly. Eventually, they get so big that they have to start using magic just to walk around without their femurs snapping--and if they live for a really, really long time, it gets to the point that they can only fly or do heavy physical activity for short periods before they have to regain their strength. The very oldest of dragons even have to undergo torpor--a period of dormancy during which they build up their magic reserves for increasingly rare periods of activity.

Dragon eggs are abandoned by their parents--they leave clutches of eggs in suitable, secluded nesting sites, but the hatchlings are left to fend for themselves. While there is a lot of variation in mindset among young dragons, the roar-smash-burn variety tend to die young. The only dragons that live to old age are the ones that invest, early on, in hoards of magic that they can tap, enchanted lairs, and so on: all the others get killed, either when they get too old to fight off younger rivals with more endurance, or when a dragonslayer catches them at their weakest.

Eh.

These kinds of patch job based, "they need magic to exist" explanations always feel clunky and too sci-fi to me.

it treats magic as an undifferentiated universal fuel for things to happen rather than as something of wonder, poetry and well.....actual magic and mysticism. reduces it to omni-applicable electricity without any defining characteristics or mystical elements, nothing more than a synonym for energy. that and somehow the world returns to a base state that somehow resembles our own without it.

especially when many rpgs (this is roleplaying games general, so not only DnD) has dragons just....exist. there is often no explanation like this to "justify" them, they are just there, with no canon or mechanics saying they need magic to exist, and IN DnD, dragons can fly in an anti-magic field canonically so them being powered by magic doesn't make sense. if dragons were truly magical like that, a wizard could simply cast dispel magic on them to make them fall apart under the strain of the duct tape being removed from the equation, they wouldn't require something like a dragon slayer to kill them, they'd just be organic machines running on magic bubblegum that could at any time collapse from anyone who knows enough to take out the right cog in the machine-same with every other creature that "shouldn't be able to exist" but does, as the same principle would apply to EVERY creature that runs on the same logic, you'd effectively be consigning most fantasy creatures to being easily defeated by a single casting of a 3rd level spell or similar counter magic in any other rpg, when this doesn't make sense with the rules or fiction being emulated.

because the thing about magic that everyone ignores is that its inherently fragile. its easy come, easy go. what can be conjured or made from nothing can just as easily be dispelled or erased back into nothing. Its incredibly manipulable like that. most stories with magic where someone gets cursed? has ways to reverse that curse. people that are possessed can in turn be exorcised. a spell that can be cast can be counter-spelled to never occur and any enchantments you place on something can be disenchanted. many spells have time limits in minutes or hours so they don't last very long. What can be turned on, can be turned off. By tying fantasy creature biology to magic and trying magic into a universal framework of magic that a wizard can manipulate, you allow them to be manipulated by the same on-off logic, when its not baseline archetypal assumption that they are, the archetype is that dragons exist and to slay them requires actual slaying them like any other being.

[PhoenixPhyre]

Eh.

These kinds of patch job based, "they need magic to exist" explanations always feel clunky and too sci-fi to me.

it treats magic as an undifferentiated universal fuel for things to happen rather than as something of wonder, poetry and well.....actual magic and mysticism. reduces it to omni-applicable electricity without any defining characteristics or mystical elements, nothing more than a synonym for energy. that and somehow the world returns to a base state that somehow resembles our own without it.

especially when many rpgs (this is roleplaying games general, so not only DnD) has dragons just....exist. there is often no explanation like this to "justify" them, they are just there, with no canon or mechanics saying they need magic to exist, and IN DnD, dragons can fly in an anti-magic field canonically so them being powered by magic doesn't make sense. if dragons were truly magical like that, a wizard could simply cast dispel magic on them to make them fall apart under the strain of the duct tape being removed from the equation, they wouldn't require something like a dragon slayer to kill them, they'd just be organic machines running on magic bubblegum that could at any time collapse from anyone who knows enough to take out the right cog in the machine-same with every other creature that "shouldn't be able to exist" but does, as the same principle would apply to EVERY creature that runs on the same logic, you'd effectively be consigning most fantasy creatures to being easily defeated by a single casting of a 3rd level spell or similar counter magic in any other rpg, when this doesn't make sense with the rules or fiction being emulated.

because the thing about magic that everyone ignores is that its inherently fragile. its easy come, easy go. what can be conjured or made from nothing can just as easily be dispelled or erased back into nothing. Its incredibly manipulable like that. most stories with magic where someone gets cursed? has ways to reverse that curse. people that are possessed can in turn be exorcised. a spell that can be cast can be counter-spelled to never occur and any enchantments you place on something can be disenchanted. many spells have time limits in minutes or hours so they don't last very long. What can be turned on, can be turned off. By tying fantasy creature biology to magic and trying magic into a universal framework of magic that a wizard can manipulate, you allow them to be manipulated by the same on-off logic, when its not baseline archetypal assumption that they are, the archetype is that dragons exist and to slay them requires actual slaying them like any other being.

Here's the thing. Anti-magic field is, really, a misnomer. And a name that confuses things. As is Dispel Magic. Specifically, the names are part of the hubris of wizards, thinking that spells == magic and that magic == spells.

It doesn't. Those effects? They disrupt organized, artificial uses of magic. Not magic itself--no human is that strong. And if they were, the powers that be would smack them down right quick. Because magic is the stuff of existence in a D&D-like. It's in and through everything. It's as much a part of fantasy reality as the strong force is a part of our reality. And stopping it entirely is like stopping the strong force--BAD THINGS HAPPEN. Instead, those spells merely prevent and dampen existing resonant manifestations of manipulated magic (aka spells and suchlike), like a jamming device prevents coherent radio signals on the covered band by flooding the airways or like oil dampens waves by changing the surface tension. A summoned creature is fundamentally different from a natural one--the summoned one's body is made up of active spell-work, which cannot exist in the jamming zone.

Spells =/= magic. Or, said another way, the "magic" we're talking about here isn't the same as "the thing wizards do when they cast spells". It's the sum total of all fantastic nature of the setting, all the ways that the fundamental properties of the setting differ from those of our reality.

[Mechalich]

These kinds of patch job based, "they need magic to exist" explanations always feel clunky and too sci-fi to me.

I think there's an important point of differentiation between 'they needed magic to be created' and 'they need magic to exist as an ongoing concern.'

A lot of fantasy creatures violate the viable properties of biology as life evolved on earth rather than any sort of any inherent physical limits as applied to structures created using organic molecules. Evolution, though capable of spectacular things, has distinct innovation limits. For example, all life on earth uses the same 22 amino acids, even though human chemistry has discovered that many, many more exist and that natural processes are capable of producing them. And who knows what an alternative biochemistry capable of utilizing these different molecules would be capable of?

It is very possible, in fact extremely likely, that a designed organism would be capable of exceeding the capacity of evolved ones in achieving certain traits (in fact one of the more powerful pieces of evidence for evolution is how its legacy means your body is full of absolutely terrible bits of design like the recurrent laryngeal nerve). As such, if we accept that fantasy creatures like dragons and giants were designed by deities or some sort of similar extremely powerful and knowledgeable being (games like D&D have things like Elohim and Sarrukh and so on to fill this role), a modified designed anatomy and physiology can be structured to allow them to bypass existing limits. This is 'magical' in the sense that some outside force created these lifeforms using tools otherwise unavailable to those within the setting, but there no active magical effects like spells or enchantments are needed for the creatures to survive.

Of course there is a difference between basic function and the use of blatantly supernatural abilities. A good example is something like a Basilisk. A Basilisk is basically just a Komodo Dragon sized lizard that form some reason has eight legs instead of four (which is something that could probably be engineered in a lab today if you put enough money behind it), except for the petrification gaze, which is a blatantly supernatural ability that obviously requires some kind of magic to function.

[Notafish]

Generally, when one has normal and fantastical elements in a fantasy world and the fantastical elements seem to have problem with real world physics, the last thing i would attempt is trying to change the physics of the fantasy world to allow the fantasy elements. Because as a result you can basically be certain that now all the normal stuff doesn't work anymore.

Conversely, "space-time is different in the Feywild" gives you a convenient, sciencey-sounding excuse for when the fantastical elements don't fit with standard physics. Unless you really dive into it, it's just a pallete-swap of "a Wizard did it", but it does have the potential advantage of giving you a ruleset that most people know the basics of, whereas if you build rules of magic to accommodate the weirdness of the setting, you might need to spend more time world-building.

I don't think most people are as likely to ask about why the "normal stuff" doesn't work because we are all familiar with how things work in our world - I think OP's question is far more likely than, "if this universe can support dragons and giants, why are the rules for humanoids based on what humans can do in reality?" (We save that question for arguments about martials vs. casters.)

Admittedly, saying that a more-earthlike setting like Middle Earth has low gravity would probably lead to questions about whether jump distances should be longer. I doubt it would lead to many questions about whether the dwarves should be lankier.

[Mechalich]

Conversely, "space-time is different in the Feywild" gives you a convenient, sciencey-sounding excuse for when the fantastical elements don't fit with standard physics. Unless you really dive into it, it's just a pallete-swap of "a Wizard did it", but it does have the potential advantage of giving you a ruleset that most people know the basics of, whereas if you build rules of magic to accommodate the weirdness of the setting, you might need to spend more time world-building.

Different planes certainly allow for all kinds of variance, and questions like this more or less disappear once you've hit 'we're not in Kansas anymore' territory. And you can backfill based on that, by saying that extraplanar beings somehow 'bubble' the properties of their plane along with them while on the Prime Material. This often leads to the question of 'what does the giant's sword weigh' not mattering at all because it sublimates back into another dimension when the giant dies.

Unfortunately, that sort of answer really doesn't work regarding creatures that are supposed to be integrated into the actual ecology of the fantasy world.

Admittedly, saying that a more-earthlike setting like Middle Earth has low gravity would probably lead to questions about whether jump distances should be longer. I doubt it would lead to many questions about whether the dwarves should be lankier.

Science fiction settings that deal with low gravity worlds actually tend to talk about that question a lot, and D&D does have rules for low and high gravity environments, just not very detailed ones because characters aren't expected to spend much time in them.

[Necroanswer]

I think a lot of people are still missing the point. I'm still seeing a lot of "just don't worry about it" or "it's fantasy it doesn't need to be like real world physics" or "here's a lore justification for why this works," etc.

If it has a Strength score, and a listed size, then it has a defined carrying capacity. What isn't defined is (a) the weight of the creature, and (b) the weight of their equipment. I can "not worry about it" up until one of the players attempts to pick up a giant, or loot the giant's gear, and then I need to assign a weight to these things. And if it ends up, as one other user so poetically put it, that the giant can't lift their own pants, it's an instant break in immersion for everyone. But it's also equally immersion breaking if it turns out those pants are lighter than air (though in fairness, maybe fantasy physics makes this not matter, i.e. the pants won't float).

So the real issue is needing to assign a real, tangible weight value to an item (or creature), and how that weight value might interact with a giant-sized creature's carrying capacity. I'm not looking for a justification for why the giant doesn't collapse under his own weight, I'm trying to figure out how to avoid a situation where the giant can't lift his own pants.

I'm kinda onboard on "don't worry about it" and think you should consider thinking that way too. If "regular" sized pants weigh 1 lb and someone picks up a 12' giants pants isn't saying its 8 lbs good enough? (Or you could use a 6x factor if you feel the thickness of a giant's equipment wouldn't scale up proportionately). You could just assume that giants could use giant sized objects irregardless of what a game manual says their strength score is. If you stop assuming they can handle proportionally sized objects you undercut the usual fantasy of giants being strong and fearsome. You can assume that they have the strength to do basic stuff what smaller folk can do: stand, walk and run without breaking bones, jump without crippling themselves, etc. I can't image many players objecting this approach.

If you have a giant sized PC I could understand being a little more concerned. If I remember correctly GURPS used a simple approach: the factor the giant's strength is increased by is also the factor by which their equipment weight increases. The solution may not stand up to close scrutiny: a base 20 strength 12' giant's equipment would only weigh x2, but you can tell players you doing it that way for play-ability rather than trying to realistically reflect what the equipment actually weighs.

[AdAstra]

Even creating a worst case scenario with everything scaled up exactly, the rules work decently enough for giants.

Assuming that a giant fills out their space the same way that a human does (which is broadly fine for the listed height for most giants) and are thus 3 times larger in every dimension (and assuming the same density, let's just say that however their physiology handles their size has more to do with strength to weight ratios and behavior than proportions), that would make them 27 times heavier. Assuming their gear was sized to exactly human proportions, that would also be 27 times heavier. Here's a list of some basic equipment and how heavy they'd be at that scale, mostly drawing from things Giants are listed as carrying or things they might reasonably be expected to have:

Spoiler: Stuff

Show

Rations: 2 lbs.> 54 lbs.
Common Clothes: 3 lbs.> 81 lbs.
Greatsword: 6 lbs.> 162 lbs.
Greatclub: 10 lbs.> 270 lbs.
Backpack (including full capacity, which is also scaled up): 35 lbs.> 945 lbs.
Scale Mail: 45 lbs.> 1215 lbs.
Plate Armor: 65 lbs.> 1755 lbs.

But giants do have 4 times the carrying capacity of a medium-sized creature due to their size, so while this stuff is definitely proportionately more of their carrying capacity, it's usually not enough for the rules to outright break. Of giant statblocks, I think only the Fire Giant (1500 lbs. carrying capacity) has enough stuff listed as to exceed its carrying capacity due to wearing Plate and not being too high in strength. The Storm Giants (1740) are the only others to wear armor with a listed weight, but it's Scale and they're stronger, so they have a little bit of capacity left over. But this again assumes that say, the plate is three times thicker than human-scale plate, rather than being the same or not as much greater thickness over a greater area, which would bring it well within their capacity. So I think even the extreme abstraction of the existing rules deals with this decently enough, giants don't have issues with pants at least.

Can probably assume most objects scale cubically, and for more 2D-oriented objects like armor, clothes, tabletop RPG books, etc. to scale somewhat less (perhaps +50% thickness for every +100% in other dimensions, so double the size means only 6 times the weight rather than 8), and still adhere to the rules just fine. Giants will not be able to carry as many giant-sized things as humans can carry human-sized things, and things will be relatively more fragile, which is close enough to what you'd expect from real world physics.

[Mechalich]

Can probably assume most objects scale cubically, and for more 2D-oriented objects like armor, clothes, tabletop RPG books, etc. to scale somewhat less (perhaps +50% thickness for every +100% in other dimensions, so double the size means only 6 times the weight rather than 8), and still adhere to the rules just fine. Giants will not be able to carry as many giant-sized things as humans can carry human-sized things, and things will be relatively more fragile, which is close enough to what you'd expect from real world physics.

I think you can be a lot more generous with the thickness, at least for certain items. Consider some like like sailcloth. You can massively increase the length and width without increasing thickness at all, and if you're a giant there's really no need to wear any clothing thicker than that, because it wouldn't be any weak for being larger.

What I think you would get is a lot of objects that appear fragile even though they've roughly the same strength as objects humans use or in fact somewhat greater strength. So you'd have items kin of like Sephiroth's Masamume - which looks ridiculous but is actually not in the hands of someone strong enough to wield one. Shadiversity actually made a wooden version of that thing and it waved around in a surprisingly practical way. A giant's weapon is likely to be more in that line. After all, the don't need something absurdly large and heavy because the things they are trying to cut/stab might be bigger than a human opponent, but they are not appreciably more solid.

[Grim Portent]

The simplest answer to the issue is to try and tone down how giants and other massive creatures look and act to be more in line with real world biology. You don't have to go all the way, but the square-cube law and real world biology can contribute to world building. Of D&D giants, hill giants are probably the most sensible, though their proportions could use some work.

Giants should largely wield no weapons beyond crude cudgels and clubs, and likely wear little to no clothing. Their hands are too large to fashion tools or do anything along the lines of fabric weaving or stitching, the materials just can't stand up to the manipulations a giant is capable of. When they have tools or proper clothing (more than furs draped across the body or crudely stitched together) it's because humans or other humanoid creatures made it for them, either as payment or under duress. The relative difficulty they would have creating clothes would probably result in giants being rather hairy, at least partially covered in fur.

Sensible weapons would be simple bludgeons. The effort involved in making a spear is probably not going to be worth it, a giant is big enough that it could kick a rhino to death and eat it raw, a log or big rock provides all the leverage and weight it needs. Captive, slaving, or cooperative giants would probably have polearms of some description, I would presume blunt ones personally, they scale better than swords, and a long wooden pole with a metal cap on one end is a perfectly capable weapon. They also take far less metal to make, which is important. Bows are basically impossible because getting the materials on the right scale and able to withstand the forces involved is not practical, so slings and throw objects would be the best weapons. A big rock or metal ball hurled by a giant might not be the most accurate weapon, but it's going to easily cave in a human's chest.

I'm not sure how much a giant sized billhook or similar weapon would weigh in practice, but it's probably not hard to work out for someone who knows the material strengths required to handle the forces involved.

They should probably have a relatively slow metabolic system, geared towards eating mostly vegetation. They have a huge and long gut by virtue of their size, which is by happy coincidence suited to digesting tough fibrous plants, which in turns reduces environmental strain. Meat, bones, fruits and so on are part of their diet, but it could be assumed that eating a lot of them would make them sick, existing land dwelling megafauna eat lots of grasses, leaves and tree bark and would suffer health problems if they ate as much fruit as humans or some primates relative to body mass This. doesn't mean a giant would be slow by any means, they would move very fast when they want to, but they would spend a lot of time eating or sleeping, appearing lazy and gluttonous to a human.

The big difference to how giants should look under the square-cube law is that they should be noticeably less humanlike. Shorter, thicker legs. Hoof like dermal pads on their feet similar to elephants, reduced or absent toes. Long arms, capable of knuckle-walking (upright bipedal motion is not kind to the body even when it's man-sized, elephant-sized exacerbates so many problems.) Proportionally smaller thumbs. They would probably look like something between a gorilla and a megasloth.

The bigger a giant is the less like a human it would look, and likely the more like an animal it would behave. A human the height of a giraffe would break down easily and struggle to meet caloric needs, a gorilla that size is more reasonable.



The other option is of course to integrate magic into giants in one of various ways, some of the old mythological versions could change size, spending a lot of their time in the size of humans and becoming giant when travelling or fighting, with their clothing and weapons changing with them.


Dragons, similarly, could work with a few qualifiers. Quetzalcoatlus was as tall as a giraffe (and weighed approximately 1/4 to 1/8 as much) and is generally believed to have been able to fly. A medieval dragon, such as is portrayed in paintings of St. George, would be quite feasible, though it would need bigger wings than is usually depicted to be able to fly. Notably it's only the size of a horse or a lion, sometimes even just a large dog, which is a lot smaller than the elephant+ sized creatures dragons have become over time.

[Mechalich]

They should probably have a relatively slow metabolic system, geared towards eating mostly vegetation. They have a huge and long gut by virtue of their size, which is by happy coincidence suited to digesting tough fibrous plants, which in turns reduces environmental strain. Meat, bones, fruits and so on are part of their diet, but it could be assumed that eating a lot of them would make them sick, existing land dwelling megafauna eat lots of grasses, leaves and tree bark and would suffer health problems if they ate as much fruit as humans or some primates relative to body mass This. doesn't mean a giant would be slow by any means, they would move very fast when they want to, but they would spend a lot of time eating or sleeping, appearing lazy and gluttonous to a human.

The best metabolic comp for a giant is probably large bears. Several extinct bears, such as Arctodus simus and Arctotherium angustidens may have topped 1,000 kg (2,200 lbs.) in mass, and may have been 10-15 ft tall when they chose to stand solely on their hind legs. That's very comparable to the numbers given for Hill, Stone, and Frost Giants. These bears are presumed to have been omnivores with herbivory dominant in their diet. Of course bears 'hibernate' which giants are unlikely to do, and they would likely compensate by having a lower metabolic rate overall, as sloths do.

Dragons, similarly, could work with a few qualifiers. Quetzalcoatlus was as tall as a giraffe (and weighed approximately 1/4 to 1/8 as much) and is generally believed to have been able to fly. A medieval dragon, such as is portrayed in paintings of St. George, would be quite feasible, though it would need bigger wings than is usually depicted to be able to fly. Notably it's only the size of a horse or a lion, sometimes even just a large dog, which is a lot smaller than the elephant+ sized creatures dragons have become over time.

Dragons are very much helped by postulating some kind of extremely strong but also incredibly light bone structure - Skyrim, with dragonbone as an incredibly hard but also light material has the right idea - that would allow them to be bigger without necessarily being much heavier. Modern birds already do this with their 'hollow bones' and there's evidence that pterosaurs had similar adaptations, but it could definitely be taken further. I think its possible to talk about a flight capable dragon up to around 500 kg (which would be big enough to potentially carry a single small rider) assuming some precision engineering (the dragons of Pern, notably, are the product of very advanced genetic engineering, which helps), but the animal would be much more spindly looking compared to traditional fantasy art of dragons - which tends to draw dragons using a feline body covered in scales with wings just sort of glued on.

I would note that if you take away flight and just do landwyrms (or just take away the wings and make flight explicitly magical and not tied to any biological outputs) then all the problems disappear. Large quadruped archosaurian predators were a thing on Earth, in the form of the rauisuchians.

[PhoenixPhyre]

The simplest answer to the issue is to try and tone down how giants and other massive creatures look and act to be more in line with real world biology. You don't have to go all the way, but the square-cube law and real world biology can contribute to world building. Of D&D giants, hill giants are probably the most sensible, though their proportions could use some work.

Giants should largely wield no weapons beyond crude cudgels and clubs, and likely wear little to no clothing. Their hands are too large to fashion tools or do anything along the lines of fabric weaving or stitching, the materials just can't stand up to the manipulations a giant is capable of. When they have tools or proper clothing (more than furs draped across the body or crudely stitched together) it's because humans or other humanoid creatures made it for them, either as payment or under duress. The relative difficulty they would have creating clothes would probably result in giants being rather hairy, at least partially covered in fur.

Sensible weapons would be simple bludgeons. The effort involved in making a spear is probably not going to be worth it, a giant is big enough that it could kick a rhino to death and eat it raw, a log or big rock provides all the leverage and weight it needs. Captive, slaving, or cooperative giants would probably have polearms of some description, I would presume blunt ones personally, they scale better than swords, and a long wooden pole with a metal cap on one end is a perfectly capable weapon. They also take far less metal to make, which is important. Bows are basically impossible because getting the materials on the right scale and able to withstand the forces involved is not practical, so slings and throw objects would be the best weapons. A big rock or metal ball hurled by a giant might not be the most accurate weapon, but it's going to easily cave in a human's chest.

I'm not sure how much a giant sized billhook or similar weapon would weigh in practice, but it's probably not hard to work out for someone who knows the material strengths required to handle the forces involved.

They should probably have a relatively slow metabolic system, geared towards eating mostly vegetation. They have a huge and long gut by virtue of their size, which is by happy coincidence suited to digesting tough fibrous plants, which in turns reduces environmental strain. Meat, bones, fruits and so on are part of their diet, but it could be assumed that eating a lot of them would make them sick, existing land dwelling megafauna eat lots of grasses, leaves and tree bark and would suffer health problems if they ate as much fruit as humans or some primates relative to body mass This. doesn't mean a giant would be slow by any means, they would move very fast when they want to, but they would spend a lot of time eating or sleeping, appearing lazy and gluttonous to a human.

The big difference to how giants should look under the square-cube law is that they should be noticeably less humanlike. Shorter, thicker legs. Hoof like dermal pads on their feet similar to elephants, reduced or absent toes. Long arms, capable of knuckle-walking (upright bipedal motion is not kind to the body even when it's man-sized, elephant-sized exacerbates so many problems.) Proportionally smaller thumbs. They would probably look like something between a gorilla and a megasloth.

The bigger a giant is the less like a human it would look, and likely the more like an animal it would behave. A human the height of a giraffe would break down easily and struggle to meet caloric needs, a gorilla that size is more reasonable.



The other option is of course to integrate magic into giants in one of various ways, some of the old mythological versions could change size, spending a lot of their time in the size of humans and becoming giant when travelling or fighting, with their clothing and weapons changing with them.


Dragons, similarly, could work with a few qualifiers. Quetzalcoatlus was as tall as a giraffe (and weighed approximately 1/4 to 1/8 as much) and is generally believed to have been able to fly. A medieval dragon, such as is portrayed in paintings of St. George, would be quite feasible, though it would need bigger wings than is usually depicted to be able to fly. Notably it's only the size of a horse or a lion, sometimes even just a large dog, which is a lot smaller than the elephant+ sized creatures dragons have become over time.

That is, completely change how all of them are from the ground up. If I saw any of that in a D&D game, I'd say "not a giant" and "not a dragon". And you'd need radically different
* lore
* stat blocks
* world-interactions
* etc.

Sure, you can make them work by being basically large animals and stripping off everything that makes a D&D dragon a D&D dragon or a D&D giant a D&D giant. We saved the giants by destroying the giants. Yay.

And this is in a world where real-world physics, biology, chemistry, and everything else has already been tossed aside. Because that's the starting price for having spell-casting at all--it's fundamentally incompatible with the baseline rules that describe our reality. And can't be simply said to be "exceptions", because it's woven into the core of these worlds.

It's much more honest and useful to accept that difference and see where it leads, rather than trying to break everything on a bed of procrustes called "realism".

[Grim Portent]

That is, completely change how all of them are from the ground up. If I saw any of that in a D&D game, I'd say "not a giant" and "not a dragon". And you'd need radically different
* lore
* stat blocks
* world-interactions
* etc.

Sure, you can make them work by being basically large animals and stripping off everything that makes a D&D dragon a D&D dragon or a D&D giant a D&D giant. We saved the giants by destroying the giants. Yay.

And this is in a world where real-world physics, biology, chemistry, and everything else has already been tossed aside. Because that's the starting price for having spell-casting at all--it's fundamentally incompatible with the baseline rules that describe our reality. And can't be simply said to be "exceptions", because it's woven into the core of these worlds.

It's much more honest and useful to accept that difference and see where it leads, rather than trying to break everything on a bed of procrustes called "realism".

If someone is asking for how giants would make sense with the square-cube law, then D&D giants, which emphatically don't make sense, have already lost their merit for that person's hobby and should be broken over the knee and cast aside when answering their questions.

Personally Hill Giants are the only D&D giants I care about anyway, and they would essentially just need shorter, thicker legs, a bit of fur and a propensity for sitting around chewing tree bark when nothing more digestible is readily available.