When a pokemon is confused, whats the chance of them damaging themselves?

Question

My pokemon always seem to hurt themselves when confused :S

Answer 1

The confused condition causes a Pokémon to hurt itself in its confusion 50% of the time. The damage is done as if the Pokémon attacked itself with a 40-power typeless physical attack.
Confusion wears off after 1-4 attacking turns.

Straight from bulbapedia.And with Prankster its priority :)