System for calculating CRs from scratch?

[johnsemlak]

Where in the core books, or elsewhere, is there a system for calculating the CR of a creature from total scratch, if you made your own monster for example. I found the rules for NPC CRs in the DMG (page 170 or something) but that's mainly for standard human/humanoid types.

 

[Kweezil]

CRs have always been presented as more an art than a science. That said, there was a rough CR guestimator from an old issue of Dragon (#276, I think).

Divide the creature's hps by 3.5 to get a rough HD equivalent, add 1-3 HD equiv for each special ability or quality, and divide the total by 3. Just make sure to play-test it, as it's a very rough estimator.

 

[the Jester]

About that playtesting: CRs seem to assume that the party includes one optimal character against the enemy (i.e. animals are figured for the party having a druid or ranger, undead are figured for the party having a paladin or cleric, etc).

 

[EricNoah]

There was a Challenge Rating "Guestimator" presented in Skip Williams' "How to Build a Monster" article in Dragon Magazine a couple of years ago. I think, possibly, that article is available as a PDF on the WotC website. I'll take a look and see if I can find it.

 

[(Psi)SeveredHead]

Here's a good one: http://mwtools.thyle.net/race_gen.html

Savage Species is rumored to have one as well, but no one will actually if there really is one or not, and if it's better than the Sage's article.

PS that article is available as a .jpg file... somewhere. I don't remember where.

 

[Upper_Krust]

Hi all!

This might help.

http://enworld.cyberstreet.com/showthread.php?s=&threadid=45989

 

[Grazzt]

CRs have always been presented as more an art than a science. That said, there was a rough CR guestimator from an old issue of Dragon (#276, I think).

Divide the creature's hps by 3.5 to get a rough HD equivalent, add 1-3 HD equiv for each special ability or quality, and divide the total by 3. Just make sure to play-test it, as it's a very rough estimator.

Actually, according to the article you divide its total hp by 4.5, not 3.5

But, yeah, after that, according to Skip's article, you add +1 or +2 for each Special Attack or Special Quality it has. Take that final result and divide by 3. This gives the creature's CR...more or less.

But, like Kweezil said...playtest it to be sure.

 

[kreynolds]

This might help.

http://enworld.cyberstreet.com/showthread.php?s=&threadid=45989

I definately recommend UK's system. It's very easy to figure out, and while its still being developed, its very accurate. I look at CR estimation like this: Wizard's uses 15% math and requires 85% playtesting; UKs system uses 85% math and requires 15% playtesting. That's much better in my book.

 

[Marimmar@Home]

I actually found the old 2e XP calculation charts to be helpful. Just figure out the monsters modified HDs and divide by 2. This usually works fine.

~Marimmar