From your Pokémon's CP and its IVs (what are Pokémon IVs?), this calculator works out its level and how close it is to perfect, with its in-game appraisal stars.
It also shows what it would reach if you powered it up, and the Stardust, Candy and XL Candy that costs, what each evolution would be, its best movesets, and where its IVs rank for Great League and Ultra League.
Step 1: Choose your Pokémon.
Step 2: Enter its CP.
Step 3: Appraise it in the game, and set the Attack, Defense and HP bars to match the bars it shows.
Step 4: Click 'Calculate'.
If no level gives that CP with the IVs you entered, the calculator suggests the nearest IVs that do. It's easy to be a point out when reading the appraisal bars.
Each Pokemon has 3 separate IVs: these are hidden values between 0 and 15 for the Attack, Defense, and Stamina stats. These values determine how powerful a Pokemon will be at its maximum level.
Not all Pokémon are equal: two max-level Pokémon can have different IVs, resulting in one which will be more powerful then the others. For example, a level 40 Lapras can have a CP of between 2,229 and 2,603.
This means that in the worst case, you could end up with a Lapras which is only 85% as powerful as it could be!