I need one
Here (showdown) - the ultimate damage calculator, it can calculate every single generation, including 1!
Here's one for gen 5 (PokeDS)
Here's one for gen 4 (Serebii)
Pokemon Showdown's Damage Calculator
Psypoke's Damage Calculator
Since this could easily be looked up on Google, I will give you a page of Pokemon DMG Calculators here.