See also: Feats
You can make exceptionally powerful melee attacks.
Prerequisite: Strength 13
Effect: On your turn, before making an attack roll, you may choose to subtract a number from all melee attack rolls and add the same number to all melee damage rolls. This number may not exceed your Base Attack Bonus. The penalty on attacks and bonus on damage rolls applies until the start of your next turn.
Special: If you attack with a two-handed weapon, or with a one-handed weapon wielded in two hands, instead add twice the number subtracted from your attack rolls to your damage rolls. You can't add the bonus from Power Attack to the damage dealt against an object or Vehicle.