({[IV+2*Base Stat+([EVs]/4)+100] * Level}/100)+10
This is the formula for HP. For any other stat, just replace the 10 with 5m then multiply by 1.5 if your pokemon has a beneficial nature for that stat, or by .5, and times 1 for a neutral nature.
In Generations I and II:
In Generation III onwards:
The exception to this is Shedinja, whose HP will always be 1.
Stat (Bulbapedia)
If you don't know what stat experience, DVs/IVs, or EVs are, please reference the ever-helpful Bulbapedia.
