PvP Power Up Calculations
With the CP caps in these leagues, people are going to want to get as close to the cap as they can. I've been holding onto a bunch of unpowered up mons, with a few in the 2400s (e.g. Mew at 2464) I was wondering if there was a way to tell how much CP pokemon will jump when you power it up for those close to the caps.
Answers
And until that update comes out, the easiest way is to use this site's calculators. Put in your CP, HP, and dust, evaluations if you like, and then pick the IV combination that makes the most sense. Click on CP calculator (on the right) for that combination of IVs, and it takes you down to a screen where you can calculate power-ups or evolutions (or both) to see where you would land.
Last night I calculated that a level 20 Shroomish with CP 442 would evolve to a Breloom with CP 1499. CP 421 would require 1 power up to get there, CP 400 (exactly) would require 2. That gives me 3 targets for shroomish if I want to get a good Breloom for the Great League. Going down in steps of 21 works too.
Just be sure you have the right IV combination. Different IVs will all be close in final CP, but there's a huge difference between 1499 and 1501, so when you're really close, check carefully before spending dust or candy.