Each weapon, spell, and harmful monster ability specifies the damage it deals. You roll the damage die or dice, add any modifiers, and apply the damage to your target. Magic weapons, special abilities, and other factors can grant a bonus to damage. With a penalty, it is possible to deal 0 damage, but never negative damage.

When attacking with a weapon, you add your ability modifier — the same modifier used for the attack roll — to the damage. A spell tells you which dice to roll for damage and whether to add any modifiers.

If a spell or other effect deals damage to more than one target at the same time, roll the damage once for all of them. For example, when a wizard casts Fireball or a cleric casts Flame Strike, the spell's damage is rolled once for all creatures caught in the blast.