Determining CR of a group of monsters?

[WerePox47]

Ok so im in the process of building a hardcore dungeon for high level play and i was wondering about how to calculate the cr of a group.
For instance the room im currently building will have a fight involving a 1 CR 22, 1 CR 20 and 4 CR 19s..

[Elamdri]

Your exp is 1,740,800, which is over a CR 25 but not by much, so you're somewhere between a CR 25 and a CR 26.

[WerePox47]

ok so you just total the xp and compare that to a cr for that xp.. i see.. i was hoping for more of a cr 24.. maybe i need to drop 1 of the 19s

[Elamdri]

WerePox47 wrote:

ok so you just total the xp and compare that to a cr for that xp.. i see.. i was hoping for more of a cr 24.. maybe i need to drop 1 of the 19s

Yep!

A easy tip, it's in Chapter 12 of the CRB, but you can calculate CRs of multiple mobs of the Same CR with this table:

1 Creature CR
2 Creatures CR +2
3 Creatures CR +3
4 Creatures CR +4
6 Creatures CR +5
8 Creatures CR +6
12 Creatures CR +7
16 Creatures CR +8

[WerePox47]

I building gallowspire and this will be one of the final rooms before the tyrant.. the characters are all templated pc races or advanced monster races with levels, or will be by this time.. there also gestalt, so i think it should prove an interesting fight.. Im beginning to think i might need help running these encounters though lol..

[Are]

The unusual composition of your PC-group will make it pretty difficult to accurately determine how challenging an encounter will be (plain CRs likely won't be particularly accurate). Plus that's a pretty hard task at high levels anyway.

[WerePox47]

Im giving my party a +4ecl for determing fights.. Ill adjust that depending on how things go.. Their starting at cr 14s, so im goin to build there first fights as cr 18..

[vikingsean711]

Gestalt works out on average to be an LA+2 to PCs