A critical strike in classic WoW is a hit for extra damage; it is twice the normal damage for a melee or ranged attack and 1.5 times for a spell.
melee or ranged critical hit = 2 × normal damage
spell critical hit = 1.5 × normal damage
Before talents that raise the multiplier (Impale, Lethality, Ruin, Ice Shards and so on).
| Average melee damage with 30% crit | normal × (1 + 0.30 × 1) = normal × 1.30 |
| Average spell damage with 30% crit | normal × (1 + 0.30 × 0.5) = normal × 1.15 |
Last checked: unverified against Forever. These are the long-established values of the classic ruleset (the 1.x game of 2005-2006); World of Warcraft Forever is in beta and may differ. When you test this one in Forever, post your numbers in Theorycraft.