Trainers are currently participating in the Ultra League section of GO Battle League, which means no Pokemon over 2,500 CP. Prior to the actual battling, players will need to build a team of species within the confines of the Ultra League limit. To do so you'll need to know when to evolve certain Pokemon to keep them under 2,500 CP. Here's a list of the more commonly seen species and their evolution limits.

Adhering to the limit seems simple enough but when you do not know what CP a Pokemon will become when evolving it, it can become tricky. You'll need to know the maximum CP a particular Pokemon can be before evolving it.

One mistake and you may have a Pokemon that isn't eligible. Even worse, it's more than likely that Pokemon will be too weak to compete in Master League, too.

Experienced Pokemon Go trainer will know that species increase CP at different rates. For example, evoling Caterpie into Metapod won't increase its CP by much. Conversely, evolving Feebas into Milotic sees a drastic CP increase.

Fortunately there are Pokemon Go evolution calculators out there. Any Pokemon at any given CP can have a wide range of IVs, which means a definitive CP it will evolve into can't be shared. Therefore these calculators provide a range of the CP that it can evolve into.

Now, there's a balance between getting as close to the 2,500 CP limit and going past it. Ideally, you don't want to have to use too much precious Stardust to power it up to that limit.

On the other hand, going past it is disastrous. As such it is always better to evolve the Pokemon before powering it up. This way you get to see its moveset too. We've also made a list for the Great League CP evolution limits, too.

Courtesy of PokeAssistant, here are the CP ranges you should be looking for for some of the most frequently seen Pokemon in Ultra League:

Here are a selection of effective but slightly less popular Pokemon for Ultra League:

To be clear these are ranges, so if you want to guarantee you won't break the 2,500 CP limit you'll need to evolve them at lower CP than listed. Getting your Pokemon right on the Ultra League limit will no doubt cost you a lot of hard-earned Stardust, so try not to make any mistakes!

See the article here:

When to evolve Pokemon to keep them within the Ultra League CP limit - Dexerto