How to calculate CR

[Blaise The Magician]

How do I calculate the CR for a new monster??

Is there any better way to calculate the CR for HD advancment then the one in the monster manual??

thanks

Blaise The Magician

 

[Kae'Yoss]

I have read this on the forum here:

Take the creature's HD and divide it by 4.5

Add +1 or +2 for every SA or SQ the creature has.

Divide the result by 3, rounding down. That's the CR.



The advancement rules have been errata'ed

p. 14, Replace the Challenge Rating note with:
Each 50% increase to the creature's original HD increases the CR of a monster by 1. Doubling the HD raises the CR
by 2. Tripling the HD raises the CR by 4.

 

[dcollins]

Take the creature's HD and divide it by 4.5

I believe you meant to say "HP" (hit points -- average total) instead of "HD" in that line. It's supposed to represent a computation of effective hit dice.

 

[CRGreathouse]

That's a crude formula, to be sure. I've seen others that work much more finely - but I suppose it comes down to the question "how much effort to estimate a CR before playtesting?".

 

[Grazzt]

I believe you meant to say "HP" (hit points -- average total) instead of "HD" in that line. It's supposed to represent a computation of effective hit dice.

Yeppers- the above post should be avg hp / 4.5

 

[Grazzt]

That's a crude formula, to be sure. I've seen others that work much more finely - but I suppose it comes down to the question "how much effort to estimate a CR before playtesting?".

Agreed. It is rather crude, but that is what WotC gave us in Dragon 276. I agree though, playtesting should be the final call in setting a monster's CR. While the WotC system does pretty well (to at least give you some idea perhaps), playtesting should really help you define it in the end.

 

[Darkness]

Agreed. It is rather crude, but that is what WotC gave us in Dragon 276. I agree though, playtesting should be the final call in setting a monster's CR. While the WotC system does pretty well (to at least give you some idea perhaps), playtesting should really help you define it in the end.

*nods*
It especially breaks down at higher hp scores. Try applying it to a kraken, for example...

 

[Grazzt]

*nods*
It especially breaks down at higher hp scores. Try applying it to a kraken, for example...

Or Monstrous Vermin (scorpions, spiders, etc). Basically the best way to determine CR is through playtesting. That's how we did it for the Tome of Horrors.

 

[(Psi)SeveredHead]

I use http://mwtools.thyle.net/ as a baseline, but you must also compare the monster's special abilities to monsters of the same CR, and playtesting as well.