Damage per mana

Damage per mana, often abbreviated DPM, is the average damage divided by the mana required to cast the spell. Spells with a high DPM (efficiency) usually have a low DPS (speed) and vice versa, but there are exceptions when talent specs are accounted for. Many DoTs have an extremely good mana efficiency. However, this mana efficiency only occurs when the DoT lives through its full duration.