Pikachu in Pokémon Platinum evolves into Raichu when you use a Thunder Stone —there is no required level.

Best timing

  • Evolve it after level 26 if you want Pikachu to learn Thunderbolt first.
  • If you do not care about Pikachu’s level-up moves, you can evolve it as soon as you get the Thunder Stone.

Practical tip

For most players, level 26 is the usual stopping point because Thunderbolt is the main move people wait for before evolving.

TL;DR

Use a Thunder Stone whenever you want, but level 26 is the common “best” time to wait for first.