The higher the challenge rating (CR) number, the more powerful the enemy. Commonly four characters of a certain level are able to defeat one creature with a CR equal to the average level of the characters with a moderate amount of difficulty.
It can be viewed by examining the creature.
- Impossible (purple): 5 or more levels higher
- Overpowering (red): 3 or 4 levels higher
- Very Difficult (orange): 1 or 2 levels higher
- Challenging (yellow): same or 1 level lower
- Moderate (blue): 2 or 3 levels lower
- Easy (green): 4 or 5 levels lower
- Effortless (white): 6 or more levels lower
It should be noted that these distinctions can become largely irrelevant on some local vault servers, simply because a player can edit his character at will and/or give their character items and weapons that far surpass the damage rating system. This is also true for any server that allows a player to reach a high level because the challenge depends more on the equipment and character build than truly on their level.
The challenge rating of a creature is calculated using many sources, most notably hit dice (HD). The additive CR is calculated by multiplying a sum by the racial challenge rating modifier, obtained from the "CRModifier" column of the row for the creature's race in racialtypes.2da. The sum in question is of the following:
- HD * 0.15
- (natural armor class modifier) * 0.1
- [(total value of inventory items, excluding creature slots) / (HD * 20,000 + 100,000) ] * 0.2 * HD
- [ (hit points before constitution and feat bonuses) / (average hit points) ] * 0.2 * HD * (creature walk rate) / (player character walk rate)
- [ (total of ability scores before racial and other modifiers) / (HD + 50) ] * 0.1 * HD
- [ (total of innate levels of special abilities) / (HD + 6) ] * 0.15
- [ (total of innate levels of usable spells) / (HD + 1) ] * 0.15
- [ (innate save modifiers) / (base saves) + 1 ] * 0.15 * HD
- [ (total of CR values of possessed feats) / (HD * 0.5 + 7) ] * 0.1 * HD
The natural armor class modifier is the modifier entered directly into the creature's properties via the Toolset. Similarly, the innate save modifiers are entered directly into the creature's properties.
The average hit points are the average hit point die rolls for each class. For example, a creature having the classes outsider 7/fighter 3 (d8 and d10 hit dice, respectively) would have average hit points of 7*(8 + 1)/2 + 3*(10+1)/2, which equals 48.
The walk rates are taken from the "WALKRATE" column of creaturespeed.2da.
For this calculation, the innate level of level 0 spells is counted as 0.5 instead of 0.