Advancing monsters: CR goes up?

[Lizard Lips]

I thought I saw some sort of formula for bumping up the CR of critters when you advnace their hit die, and now I can't find it. Anybody know it?

 

[Sollir Furryfoot]

Don't quote me on this, but I believe its every time you add on a number of HD equal to their starting HD, increase its CR by 2. (Aka, a 3 HD, CR 2 creature advanced to 6 HD would be a CR 4 creature).

 

[shilsen]

The DMG (pg. 102, under "Tougher Monsters") says that for every 50% that you bump up the HD by, raise the CR by 1. The XP award also changes proportionately, as a result.

 

[Ysgarran]

This is one of those complaints about the CR system. It seems that it doesn't give the correct results in certain cases, especially in the case of some the outsiders...

Ysgarran.