Damage is any event that reduces the health of a player or entity, often by injury from attacks or environmental hazards.
Ranged and melee weapon damage against players, zombies, and animals is calculated in the following manner:
(Base Damage) × (Melee Power Attack Modifier) × (Quality Modifier) × (Hit Location Modifier) × (Armor Modifiers)
Damage is always rounded down at the end of a calculation.
Base damage and hit location modifiers
Each weapon has its own base damage values for players, zombies, and animals. With the exception of some purely explosive weapons which do not deal direct hit damage, each weapon also has a modifier for each body part of a player, zombie, and animal. Players and zombies are broken up into four hit locations: the skull (head), the spine (torso), the arms, and the legs. Animals only have three hit locations: the skull, the spine, and the limbs.
Players and zombies can wear clothing, which can provide armor. Hats, vests, shirts, and pants can all provide armor. Hats provide head armor, vests provide torso armor, shirts provide arm and torso armor, and pants provide leg armor. Only the armor from the relevant hit location is calculated. Shirts and vests can stack for damage done towards the torso.