D20 vs. D24

[Cap'n Gravelock]

Is making a game based on D24 rather than D20 feasible.

I have this idea:

Normally with d20 a natural 20 is a guaranteed hit and possible critical hit.

However with d24, 22, 23 is a guaranteed hit and 24 is a guaranteed critical hit.

Sound okay?

[Knaight]

There's nothing innate to the d24 that allows for this. You could use a d20, have 18 and 19 be guaranteed hits, and have 20 be a guaranteed crit, and get fairly similar results. Meanwhile the d20 has the advantage of being an easily obtainable actual die, if a specialty product, where the d24 is a fair bit more specialized and harder to get ahold of.

[NerdHut]

I have to agree with Knaight. The d24 doesn't offer much over a d20, and is much harder to get (at least in most places).

And to me, it just feels like a situation of "Okay, but what if we made the numbers bigger?"

There's also the concern that if you make such a large portion of the die automatic success, you don't leave as much room for level-based improvement (which, while not necessary for a roleplaying game, is considered the standard approach).

[Cap'n Gravelock]

Thanks Knaight and Nerdhut for the input.

Although we usually use dice rollers in phones around here so most of us have access to both.

Also TTRPGs aren't common where I am and they're still heavily stigmatized in some circles...

[Knaight]

Thanks Knaight and Nerdhut for the input.

Although we usually use dice rollers in phones around here so most of us have access to both.

Also TTRPGs aren't common where I am and they're still heavily stigmatized in some circles...

If you're using dice rollers that obviates access differences. This still leaves the way they just aren't particularly different rolling systems, where what you're doing with the d24 can be done just as easily with a d20. It comes down to aesthetics - and there are decent reasons to go either way there. The top 8th of results being special feels a bit better than the top 15% of results being special, 22+ is also a bit more memorable than 18+ due to the repetition, so there's that. On the other hand, 20 is a nice round number and has that aesthetic going for it, and if you favor decimal representations over fractional representations the d20 has a friendlier spread.

It's only a 20% increase in die size, which is smaller than most die increments. You're not using a mechanic which really makes that sort of thing stand out (searching for matches in a pool being the particularly blatant one), but instead roll and add, which makes them minor. It just works out to pretty insignificant.

With that said, there are some interesting quirks to the d24. Most notably, if your system uses effects off of evens, odds, increments of X, etc. the clean sets are a bit different than a d20. Where 20 is only evenly divisible by 2, 4, 5, 10, and 20 the use of a d24 gives you 2, 3, 4, 6, 8, 12, and 24. It still comes down to aesthetics for the most part (slightly uneven breaks are usually not a big deal in play), but these aesthetics are a bit more relevant.

[Grod_The_Giant]

As Knaight said, there's nothing particularly wrong with using a d24 (other than physical die availability), but it doesn't really work out much differently than a d20. Was there a particular reason you were looking at using one?

(Also, one more aesthetic concern: with a d24, passive perception, AC and the like would wind up being "bonus+12," rather than "bonus+10," which is a little less neat)

[jqavins]

Normally with d20 a natural 20 is a guaranteed hit and possible critical hit.

However with d24, 22, 23 is a guaranteed hit and 24 is a guaranteed critical hit.How would you handle attacks that have a greater threat range, whether because of the weapon type, magic weapons, or feats? Or combinations: Improved Crit or Keen on a rapier gives a threat range of 15-20. Analogously in your proposed d24 system, would the plain rapier have automatic crits on 22-24 rather than 18-20? And the Keen rapier an automatic crit on 19-24? Removing the need to confirm crits gives the keen rapier a 25% chance of a crit on every attack, assuming a 19 hits at all.

I agree with the others that changing from d20 (5% chance for any given result) to d24 (4⅙% chance for any given result) doesn't make any real difference. But eliminating crit confirmation seems ill considered.

[Cap'n Gravelock]

Thanks everyone.