How to calculate CR under 1 ?

[Condé]

Hello,

I'm having trouble figuring how to calculate Challenge Rating under CR1.

I already read How to improve monsters (https://www.d20srd.org/srd/improvingMonsters.htm) and the Urpriest's Monstrous Monster Handbook (https://forums.giantitp.com/showthread.php?207928-Urpriest-s-Monstrous-Monster-Handbook) but, otherwise I missed something, I don't see anything about CR<1.

For example, how do you calculate fractionated CR ?

A CR 1/3 with a template that give CR+1 is what ? CR 1/2 ? CR 1+1/3 ? (So not really CR1 but not really CR2 either ?)

Other practical example some of you can explain to me... The Revived Fossil Baboon.
A baboon is CR1/2. No problem. So it has 1HD. Right ?

If we look at the Revived Fossil Template we can see that 1/2 Hit dice = Cr1/3. Then 2-3 HD = CR2...
What is a 1/2 HD to begin with ? With there is no entry for 1HD ?
Why does a CR1/2 (Baboon) with a template that gives no bonus HD or modify its CR is suddenly CR1 and do not follow the table associated with the template ?

I thought I understood how all of that work... But now, I'm just... Confused.

[Quentinas]

Fractionary hit dice is generally used for creatures weak like a rat or a cat , so creature quite weak that are not so suited for combat

For the example the table should be ignored if one follow the errata (http://archive.wizards.com/default.asp?x=dnd/errata) which change in cr+3 so our revived fossil baboon would be a cr 3+1/3 (sp a cr 3 for me as it's not relevant that 1/3 for that level) and even if the hit dice doesn't increase he gain hit points a good natural armor , a claw attack (as the baboons has "hands") various immunities from the undead type.

Generally if I apply a template to a creature with a fractionary cr I approximates at the lower cr, except when it's only a +1 cr as in these case sometimes (especially with creature that have a 1/2 cr) i chose to give them a cr 2 instead of one

[GeoffWatson]

For Calculations:
CR 1 1
CR 1/2 0
CR 1/3 -1
CR 1/4 -2
CR 1/6 -3
etc

So a CR 1/3 with a +2 template would be CR 1.

Though it'd be best to do the "compare with other monsters of that CR" to see if anything is really off.

[Crake]

For Calculations:
CR 1 1
CR 1/2 0
CR 1/3 -1
CR 1/4 -2
CR 1/6 -3
etc

So a CR 1/3 with a +2 template would be CR 1.

Though it'd be best to do the "compare with other monsters of that CR" to see if anything is really off.

This is basically correct. Each +1 just reduces the fraction's denominator to the next step.

[Beni-Kujaku]

This is basically correct. Each +1 just reduces the fraction's denominator to the next step.

Note that we're talking "steps" in the D&D 3.5 sense, which is 1<2<3<4<6<8<10<12<20, which are the number of sides of the most common dice (there is no CR 1/12 or CR 1/20 creatures, but there might be with 3rd party templates. For example, a Degenerate (Book of Templates) bat (CR 1/10) might be CR 1/12 or even CR 1/20)

[ShurikVch]

For Calculations:
CR 1 1
CR 1/2 0
CR 1/3 -1
CR 1/4 -2
CR 1/6 -3
etc

So a CR 1/3 with a +2 template would be CR 1.

This is basically correct. Each +1 just reduces the fraction's denominator to the next step.
:smallconfused: Eh, I don't get it...
Please, can somebody explain me how it works?
Why not the usual rounding down?
Also, wouldn't CR 1/10 and +1 template result in negative CR?..

[Biggus]

This is basically correct. Each +1 just reduces the fraction's denominator to the next step.

I've never heard that before, where does it say that?

[Beni-Kujaku]

I've never heard that before, where does it say that?

Here is a Pathfinder source. I can't remember where it is in 3.5, but I'm pretty sure it's the same: https://www.d20pfsrd.com/gamemastering/

Under "designing encounters": "A creature that only possesses non-player class levels (such as a warrior or adept) is factored in as a creature with a CR equal to its class levels –2. If this reduction would reduce a creature’s CR to below 1, its CR drops one step on the following progression for each step below 1 this reduction would make: 1/2, 1/3, 1/4, 1/6, 1/8."

That's only for NPC class levels, but easy to generalize.



Eh, I don't get it...
Please, can somebody explain me how it works?
Why not the usual rounding down?
Also, wouldn't CR 1/10 and +1 template result in negative CR?..

Negative CR doesn't really make sense, since you are supposed to add the CR of the monsters in an encounter to get the total CR of the encounter (this doesn't really work in practice, but that's how it's described). However weak, it makes no sense that adding an opponent would reduce the total CR. So, for really weak monsters, they invented fractional CR. A monster CR 1 from which you remove HD so that it should lose one CR is roughly half as dangerous, and is described as CR 1/2, instead of the CR 0 that it would get from pure calculations. The opposite is true. CR 1/8 represents 5 "ranks" below CR 1, (1>1/2>1/3>1/4>1/6>1/8) so if you apply a +3 CR template to it, it would gain 3 "ranks" and become CR 1/3.

[Crake]

Here is a Pathfinder source. I can't remember where it is in 3.5, but I'm pretty sure it's the same: https://www.d20pfsrd.com/gamemastering/

Under "designing encounters": "A creature that only possesses non-player class levels (such as a warrior or adept) is factored in as a creature with a CR equal to its class levels –2. If this reduction would reduce a creature’s CR to below 1, its CR drops one step on the following progression for each step below 1 this reduction would make: 1/2, 1/3, 1/4, 1/6, 1/8."

That's only for NPC class levels, but easy to generalize.




Negative CR doesn't really make sense, since you are supposed to add the CR of the monsters in an encounter to get the total CR of the encounter (this doesn't really work in practice, but that's how it's described). However weak, it makes no sense that adding an opponent would reduce the total CR. So, for really weak monsters, they invented fractional CR. A monster CR 1 from which you remove HD so that it should lose one CR is roughly half as dangerous, and is described as CR 1/2, instead of the CR 0 that it would get from pure calculations. The opposite is true. CR 1/8 represents 5 "ranks" below CR 1, (1>1/2>1/3>1/4>1/6>1/8) so if you apply a +3 CR template to it, it would gain 3 "ranks" and become CR 1/3.

Maybe it was a pathfinder thing, but i swear it was in 3.5 as well.

[ShurikVch]

Found the thing:
Large Monstrous Redspotted Centipede (Dungeon #84): CR 1½*

*This centipede has 1 more Hit Die than the typical Large monstrous centipede, so award +50% XP.

[Quentinas]

So we can presume that for an hypotetical cr 1+1/4 one should award 25% more than a cr 1 , while for a cr 2+1/4 only 12,5% more? I don't know if in that dungeon magazine there are other example but one could think this

[ShurikVch]

Negative CR doesn't really make sense, since you are supposed to add the CR of the monsters in an encounter to get the total CR of the encounter (this doesn't really work in practice, but that's how it's described). However weak, it makes no sense that adding an opponent would reduce the total CR. So, for really weak monsters, they invented fractional CR. A monster CR 1 from which you remove HD so that it should lose one CR is roughly half as dangerous, and is described as CR 1/2, instead of the CR 0 that it would get from pure calculations. The opposite is true. CR 1/8 represents 5 "ranks" below CR 1, (1>1/2>1/3>1/4>1/6>1/8) so if you apply a +3 CR template to it, it would gain 3 "ranks" and become CR 1/3.
Is this RAW?
Because it causimg extremely lopsided results for a lower end of CR (you know, the end when it's really matter)
Kobold (CR ¼) WereLegendary Wolf would be just CR 2 - despite being able to wipe the floor with most lvl 2 parties (Legendary Wolf is CR 7 by itself)
Muckdweller (also CR ¼) is legal for Monster of Legend template. By this rules, it would have CR ½ (despite having spellcasting of level 5 Cleric with the Protection, Strength, and War domains)
Also, CR 0 (http://archive.wizards.com/default.asp?x=dnd/pg/20030924a) is a thing. By the aforementioned rule, +CR would be incalculable; by the "usual" rules - calculate +CR is trivial...

[noob]

Is this RAW?
Because it causimg extremely lopsided results for a lower end of CR (you know, the end when it's really matter)
Kobold (CR ¼) WereLegendary Wolf would be just CR 2 - despite being able to wipe the floor with most lvl 2 parties (Legendary Wolf is CR 7 by itself)
Muckdweller (also CR ¼) is legal for Monster of Legend template. By this rules, it would have CR ½ (despite having spellcasting of level 5 Cleric with the Protection, Strength, and War domains)
Also, CR 0 (http://archive.wizards.com/default.asp?x=dnd/pg/20030924a) is a thing. By the aforementioned rule, +CR would be incalculable; by the "usual" rules - calculate +CR is trivial...

CR 0 is not fractional so you would use the rules for integer crs.
Not that I know any rules specific to fractional crs.

[Beni-Kujaku]

Is this RAW?
Because it causimg extremely lopsided results for a lower end of CR (you know, the end when it's really matter)
Kobold (CR ¼) WereLegendary Wolf would be just CR 2 - despite being able to wipe the floor with most lvl 2 parties (Legendary Wolf is CR 7 by itself)
Muckdweller (also CR ¼) is legal for Monster of Legend template. By this rules, it would have CR ½ (despite having spellcasting of level 5 Cleric with the Protection, Strength, and War domains)
Also, CR 0 (http://archive.wizards.com/default.asp?x=dnd/pg/20030924a) is a thing. By the aforementioned rule, +CR would be incalculable; by the "usual" rules - calculate +CR is trivial...

Yes, this is RAW. Is it practical in a game? Well, I will say "as much as any other CR calculation". That Damn Crab will decimate any level 3 party, the adamantine clockwork horror and it's at-will Implosion has absolutely no right to be CR 9... Of course, applying templates only increase this discrepancy between actual power and calculated CR. And the Monster of Legend template is far, far from being only a +2 CR when used on low-level monsters. Even on a CR 1 monster, giving it 5th level cleric level and the absolute sh*tton of abilities from the template should be way more than +2.
In the end, these are valid concerns, but are mostly based on the fact that these templates kind of don't really use the base chassis. Lycanthrope gives all the stats of the animal, while MoL gives casting making the rest of the monster quite irrelevant. And always remember that CR is just a guideline, and calculated CR from several sources is an even vaguer one than regular CR is.

[Crake]

Is this RAW?
Because it causimg extremely lopsided results for a lower end of CR (you know, the end when it's really matter)
Kobold (CR ¼) WereLegendary Wolf would be just CR 2 - despite being able to wipe the floor with most lvl 2 parties (Legendary Wolf is CR 7 by itself)
Muckdweller (also CR ¼) is legal for Monster of Legend template. By this rules, it would have CR ½ (despite having spellcasting of level 5 Cleric with the Protection, Strength, and War domains)
Also, CR 0 (http://archive.wizards.com/default.asp?x=dnd/pg/20030924a) is a thing. By the aforementioned rule, +CR would be incalculable; by the "usual" rules - calculate +CR is trivial...

That's more on the lycanthrope/monster of legend rules than the fractional CR rules.

[ShurikVch]

CR 0 is not fractional so you would use the rules for integer crs.
OK, good point! :smallsmile:



Yes, this is RAW. Is it practical in a game? Well, I will say "as much as any other CR calculation". That Damn Crab will decimate any level 3 party
The lion's share of infamy for TDC came from this (http://archive.wizards.com/default.asp?x=dnd/fw/20040221a) online article; Stormwrack toned it down:
The "online" TDC have 7 HD; Stormwrack - 6
The "online" TDC have 22 Str; Stormwrack - 21
The "online" TDC have +19 grapple; Stormwrack - +17
The "online" TDC have +2 on initiative; Stormwrack - +0
The "online" TDC have 40' speed; Stormwrack - 20'
The "online" TDC have 20' swim speed; Stormwrack - no swim speed at all
The "online" TDC gets X1.5 Str for all its attacks
And, finally: the "online" TDC is CR 3; Stormwrack - CR 4
(The only things which Stormwrack kinda increased is Constrict damage: 2d8+5 vs 1d8+9; and +4 bonus on Spot checks)


the adamantine clockwork horror and it's at-will Implosion has absolutely no right to be CR 9...
Adamantine Horror is designed as a part of EL 12-14 encounter:

Organization: Assembly (1 plus 1–2 platinum horrors, 3–4 gold horrors, and 5–20 electrum horrors)
Maybe, still kinda low, but far cry from the "CR 9"


And the Monster of Legend template is far, far from being only a +2 CR when used on low-level monsters. Even on a CR 1 monster, giving it 5th level cleric level and the absolute sh*tton of abilities from the template should be way more than +2.
Well, Muckdweller of Legend have only 6 hp
One good charge, or lucky Sneak Attack - and they would be gone
Doable for 3rd-level party; for 1st-level - much more difficult...


In the end, these are valid concerns, but are mostly based on the fact that these templates kind of don't really use the base chassis. Lycanthrope gives all the stats of the animal
Then, maybe, it should give CR of the animal too?
(Or, at the very least, full-blown +5 - not that "fractional" nonsense)


And always remember that CR is just a guideline, and calculated CR from several sources is an even vaguer one than regular CR is.
But OP specifically asked for CR...

[Crake]

But OP specifically asked for CR...

While that's true, the Monster Manual does specifically say that when applying templates and modifying monsters with extra HD or classes, that you should compare the monster's stats and abilities to relevant creatures, and see if you need to adjust the CR manually for an encounter, because, as stated, CR is just a guideline. Also keep in mind that CR is for an average party with baseline expectations, but each individual party's power is on a scale, 4 characters of the same level won't have the same capabilities and strength, so what might be level appropriate for one party would be a joke for another. Ultimately, designing encounters means putting in work and playtesting, you can't just throw it into an equation and spit out a good encounter.

[Yuki Akuma]

The game needs a way to represent things that are less dangerous than CR 1, but a CR of 0 would imply that you can add as many of such creatures as you please without making the fight more dangerous, so they use fractions instead.

You calculate the CR as an integer value - 0, -1, -2, etc - and then convert it into the appropriate fraction so you can sum up the total CR of the fight.

[ShurikVch]

You calculate the CR as an integer value - 0, -1, -2, etc - and then convert it into the appropriate fraction so you can sum up the total CR of the fight.
I need explanation for this moment: usually, you just don't "calculate the CR" below 1 - they're already set (at least, for Zombies, Skeletons, and Geist)
Templates which actively subtracting from CR are not just extremely rare, but deal mostly with creatures far above the CR 1 - such as Incorporeal Sentinel (http://archive.wizards.com/default.asp?x=dnd/wn/20030521a), Nameless Dragon, or bigger Anthropomorphic Animals
The only templates (AFAIK) which may drop CR below 1 are Necropolitan Skeleton and Proto-Creature - and both of them are 3rd-party...

[Thurbane]

Maybe it was a pathfinder thing, but i swear it was in 3.5 as well.

I've never seen it before, so I'm pretty sure it is PF only.

Struggling to find a citation, but my understanding is that once you get to CR 1 or higher, fractional CRs cease to be a thing, and are, in essence, rounded down.

Although, having said that, the half-dragon entry says this:


Challenge Rating
Same as the base creature + 2 (minimum 3).

If fractional CRs above 1 aren't possible, then technically the SRD shouldn't need to spell that out for half-dragons (although it certainly wouldn't be the first case of redundant rules).


Found the thing:
Large Monstrous Redspotted Centipede (Dungeon #84): CR 1½*

Good catch, but stat blocks are often fraught with errors, so generally don't make great RAW citations.

Coupled with the fact that Dungeon Mag is (admittedly, licensed) material from a 3rd party publisher, with material written by mostly non-staff contributors...I'm not convinced how much weight that carries.

[PraxisVetli]

If the creature feels like it hits above its weight class, I'll round up.
Otherwise, I'll ignore the fraction, or simply add the appropriate amount of HD. Suppose a Magical Beast that ends up CR 5½, I'll just give it two HD and call it 6. Now the players get slightly more loot too, and they always appreciate that.

[Condé]

For Calculations:
CR 1 1
CR 1/2 0
CR 1/3 -1
CR 1/4 -2
CR 1/6 -3
etc

So a CR 1/3 with a +2 template would be CR 1.

Though it'd be best to do the "compare with other monsters of that CR" to see if anything is really off.

I see. Actually, that make sense, I guess. I was struggling so hard trying to figure how CR<1 was working, i'm pretty fine with that explanation. Wished it was clearer or people talked about CR<1 a little bit more. But I guess monsters with that CR aren't that interesting in the first place.


Is this RAW?
Because it causimg extremely lopsided results for a lower end of CR (you know, the end when it's really matter)
Kobold (CR ¼) WereLegendary Wolf would be just CR 2 - despite being able to wipe the floor with most lvl 2 parties (Legendary Wolf is CR 7 by itself)
Muckdweller (also CR ¼) is legal for Monster of Legend template. By this rules, it would have CR ½ (despite having spellcasting of level 5 Cleric with the Protection, Strength, and War domains)
Also, CR 0 (http://archive.wizards.com/default.asp?x=dnd/pg/20030924a) is a thing. By the aforementioned rule, +CR would be incalculable; by the "usual" rules - calculate +CR is trivial...

Yeah, that's the kind of things I'm afraid of and no sane DM would ever use ine the first place. Sure, most template doesn't give monsters an HD boost so it's that, but some pump monsters so much that it makes them more like glass-canon. Whoever win the initiative win the fight because the PC or the monster is going to get one shoted.

-- And a big thank you to everyone for you answers. It's really helping.

CR is not an exact science or anything and at that level, it is hard to balance things out. Plus you can't really "play-test" things, in condition I mean, because you'd have to make a lot of game to make statistics about if it's well balanced or not.
And we all know that, for the most part, CR doesn't mean anything in real-world situation. Because dice rolls. :D