In battle
Huge Power doubles the user's Attack stat. See also Pure Power.
If this ability is Skill Swapped, copied with Role Play or Traced, the effect is halved, boosting the Attack stat only by a 1.5x multiplier and not doubling. This is the only difference from the similar ability, Pure Power.
In Pokémon Mystery Dungeon and its sequel, Huge Power has a one-in-three chance of boosting a physical attack by 50% when such an attack is used.
Outside of battle
Huge Power has no effect outside of battle.