Spell Power (mage talent)

Spell Power is a Mage talent that increases spell critical strike damage bonus by 25% per rank, up to 50% at max rank. The additional damage for critical strikes makes this a popular talent for raiding mages who go deep into the Arcane tree.

Formulas
Spell critical strike bonus is normally 50% of base spell damage, meaning a spell that hits for 1000 will crit for 1500, a bonus of 500 damage. This talent increases the bonus damage by the listed percent. With two points in this talent, the bonus damage for this example would be 750, for a total crit of 1750. The following formula will compute a critical strike given base spell hit damage, where X is the number of points in Spell Power:

Crit damage = Hit damage * (1.0 + 0.5 * (1.0 + 0.25*X))

Spell Power stacks with the talent Ice Shards. With both talents at max rank, a Frostbolt that hits for 1000 will crit for 2250, a bonus of 1250 damage. The following formula will compute a Frost critical strike with both talents, where X is the number of points in Spell Power and Y is the number of points in Ice Shards:

Crit damage = Hit damage * (1.0 + 0.5 * (1.0 + 0.25*X + 0.20*Y))

Spell Power also works with the talent Ignite. In this case, the bonus damage is included in the DoT that is applied. With both talents at max rank, a Fireball that hits for 1000 will crit for 1750 and Ignite will do an additional 40% of 1750, or 700 damage. The total damage is 2450. The following formula will calculate total Fire critical strike damage (direct plus DoT) with both talents, where X is the number of points in Spell Power and Y is the number of points in Ignite:

Crit damage = (Hit damage * (1.0 + 0.5 * (1.0 + 0.25*X)) * (1.0 + 0.08*Y)