Calculating Challenge Rating

[AslanCross]

Challenge Rating is supposed to represent a monster that will be Challenging (ie, consume approximately 25% of a party's resources) in an encounter. The party should be able to fight four EL X encounters per day, where X = the party's level. This assumes everyone is of the same level and that there are four of them.

Encounter level is not simple addition, but the Encounter Calculators can do that for you.

Note however that monsters of the same CR are not necessarily equal. Even the Monster Manual admits it is not an exact science. For example, a 10th level fighter and a Juvenile Red Dragon are both CR 10. A 10th-level party won't break into a sweat with the fighter even if he might have good equipment. However, a CR 10 dragon is potentially a very difficult enemy, and I'd think both players and DM would only want to run a single dragon per day.

Sometimes, NPC classes may be BETTER than PC classes. A CR 1 Human Warrior 2 is potentially better than a CR 1 Human Fighter 1 due to better saves and BAB. The Fighter gets ahead with its extra feat, but say, Power Attack isn't really going to matter much at that level .

Ideally a party should be able to fight a monster of CR X+4, where X is their party level. These should be the exception and not the norm, or else the party will either get wiped out or gain XP too quickly. However, I've seen a 6th-level party take out an 11th-level human warblade. Humanoid opponents get shafted by the CR system, since while classes are supposed to boost their abilities much faster than advancing HD on monsters, they're usually medium (read: easily mobbed) and they only get one action vs the party's 4 or more actions.