# How much damage an attack will do to a unit?

From StarCraft AI, the resource for custom StarCraft Brood War AIs

Original article at Staredit Network Wiki

To determine how much damage an attack will do to a unit, follow these steps.

- If the unit has shield HP, subtract shield armor upgrades from the damage.
- Apply the damage to the shield HP.
- If any damage remains, subtract the unit's armor from the damage.
- If the damage is Explosive or Concussive type, modify it based on the unit's size.
- Explosive damage deals 100% to large units, 75% to medium units, and 50% to small units.
- Concussive damage deals 25% to large units, 50% to medium units, and 100% to small units.
- Apply the remaining damage to the HP. If the remaining damage is one-half or less, it will do a half-point of damage.

##### Example 1

Siege Tank (70 damage, explosive) attacks a Zealot (60 shields, 100 hit points, 1 armor)

- 70 damage is reduced by 0. (No shield armor upgrades)
- 60 shield points are removed from the zealot. 10 damage remains.
- 10 damage is reduced by 1. (Zealot base armor)
- The damage is Explosive type and the Zealot is small. 9 damage becomes 4.5 damage.
- 100 HP reduced to 96.5.

##### Example 2

Hydralisk (10 damage, explosive) attacks a Matriarch (300 hit points, 3 armor, medium size)

- 10 damage is reduced by 0. (No shield armor upgrades)
- 0 shield points are removed from the Matriarch. 10 damage remains.
- 10 damage is reduced by 3. (Matriarch base armor)
- The damage is Explosive type and the Matriarch is medium (75% damage). 7 damage becomes 5.25 damage.
- 300 HP reduced to 294.75.

##### Example 3

Ghost (10 damage, concussive) attacks a Siege Tank (150 hit points, 1 armor, large size)

- 10 damage is reduced by 0. (No shield armor upgrades)
- 0 shield points are removed from the Siege Tank. 10 damage remains.
- 10 damage is reduced by 1. (Siege Tank base armor)
- The damage is Concussive type and the Siege Tank is large (25% damage). 9 damage becomes 2.25 damage.
- 150 HP reduced to 147.75.

##### Spell Damage

All spells except for Yamato Cannon and Nuke ignore unit armor. Yamato Cannon does 260 explosive damage to a single target. Plague also ignores Protoss shields and does damage directly to the unit or buildings HP. See the 3 spell pages for full details, including damage and duration, for all spells and abilities.