How to calculate encounters with NPCs in the party?

[CasualCreative]

Hi all, I'm new here. I'm GMing for my group and I'm having trouble balancing encounters. Here's the dealio:

My players are going to be going against some baddies with tamed fire elementals and I know they can't handle those things by themselves, so they're getting help from some good-aligned NPCs. For the NPCs, I used the statblocks from Appendix B of the Monster Manual, and planning encounters with them is getting on my nerves. How do I calculate the level equivalent of NPCs which use statblocks from the MM? What level is a CR 2 Bandit Captain and how do I calculate that for other monsters and NPCs? I'm using the Kobold Fight Club to help me calculate encounters. Thanks in advanced.

[Zman]

It is really easy, just subtract the XP pool of the allies from the XP pool of the enemies, also subtract them from the number of enemies when calculating the XP multiplier for multiple enemies.

[CasualCreative]

It is really easy, just subtract the XP pool of the allies from the XP pool of the enemies, also subtract them from the number of enemies when calculating the XP multiplier for multiple enemies.

Looks like it works to me. Thanks a lot!

[Grod_The_Giant]

Treat them as PCs with levels equal to their CR, and calculate experience thresholds and numerical modifiers accordingly?

[Zman]

Looks like it works to me. Thanks a lot!

Yep, running them as a simple cancellation works just fine as they are expected to pull their weight in xp against the enemies and what is left is the party's xp encounter budget etc.