[RPG] Calculating encounter level with mixed CR enemies


In D&D 3.5 how do you calculate the Encounter Level of an encounter when the encounter involves elements (usually enemies) of multiple CRs?

For example an encounter involves

  • 4 Zombies (CR1/2)
  • 2 Ghouls (CR1)
  • 1 Ghast (CR3)

What would the CR be?

Best Answer

Rmorrisey's formula is correct, but to simplify: here's a rule of thumb: Doubles bump the EL by +2.

2 of any single monster is the same as the Base CR +2. Two CR1 monsters (the ghouls) is an EL3. (1+2=3)

The EL 3 ghouls and the CR 3 ghast are doubles, and thus an EL 5. (3+2=5)

4 CR1/2 zombies is not quite big enough to make an EL 5 (which would make this a 7, according to the double-bump principle), so it's a 6, more or less. Bigger than a 5, not quite a 7.

Here's a sideways trick you can use too: Class levels bump a full CR per level. NPC classes bump a 1/2 CR per level. As far as this formula is concerned, half CR's don't really count for much. Thus you can usually layer a single level of warrior or expert or acolyte (+1d8 hd and a +1 BAB) onto just about anything without really pushing the margin.

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