Damage is a stat that determines the the amount of health points (HPs) that will be removed from a unit upon being hit by a shot from a weapon, an explosion or some specific abilities such as Mindfray or others.
There are essentially two different ways of calculating damage in the game:
- Random damage, dealt by firearms and melee weapons (pistols, rifles, blades, claws, etc.), with the damage value being determined randomly (and specially when using Second Wave's Damage Roulette option) and the possibility of inflicting Critical Damage, or additional damage.
- Static damage, inflicted by explosives (grenades, rockets, exploding objects, etc.) or other means such as poison or Psionic abilities, which is fixed and cannot inflict critical hits.
Regarding weapons/items, each has a defined damage stat but the game uses two types of damage when performing calculations to determine the total damage inflicted upon a target:
- Base Damage, which has a fixed value but that can be either static or variable (random).
- Critical Damage, which is always random.
Random Damage only applies to firearms (conventional, laser and plasma) and can vary between -1 and +1 of the weapon's fixed Base Damage value for non-critical hits.
As an example, the Plasma Rifle on the right has a fixed value of 7 for its Base Damage, but this value randomly can vary between 6 and 8 damage upon hitting a target.
Regarding critical hits, Critical Damage can vary according to the following formula :
- Base Damage (fixed value) is increased by +1
- Result is multiplied by 1.5, any fractions are rounded down
- Result is added by a random number between 0 and 2, then subtracted by -1
Although this formula is the one used to display the Critical Damage numbers on the weapons info at the Barracks, during missions it isn't used due to a bug and the actual damage results are different than the displayed numbers. Instead of getting 3 possible results for Critical Damage, for instance the 11-13 listed for the Plasma Rifle, the game will only produce 2 results, with one having a 66% chance of occuring and the other a 33% chance. For a breakdown of the differences, see Weapons.
Damage Roulette is a Second Wave option that further increases the randomness of each weapon.
- Base Damage can vary between between 1 and the weapons' Base Damage fixed value + 50% (rounded down)
- Critical Damage adds the base damage fixed value to the previously calculated random damage.
As an example, a Plasma Rifle's Base Damage can vary between 1 and 10 (7 + 3.5, round down). Its Critical Damage can vary between 8 and 17 (1 to 10, plus 7).
Damage Values Display
On vanilla EU, the weapon info box will only display the Base Damage's fixed value and the lower value for Critical Damage. However, on the Enemy Within DLC, the box will display the range of possible values for both Base and Critical Damage.
During tactical combat, the game will also give information about the weapon's Base Damage when pressing fire. The number displayed will be the maximum Base Damage possible.
On the Enemy Within DLC, the information about the weapons that can be seem at the Barracks is clearly incorrect for some weapons regarding their actual Critical Damage values due to a bug previously mentioned. Some examples are listed below:
- Assault Rifle & Plasma Pistol: Critical Damage listed as between 5-7, actual values are 4-6.
Some class abilities or Foundry upgrades will increase/reduce the damage output of a unit or its weapon.
- Headshot: +2/2/3 Damage to Sniper Rifle, depending on weapon tech value.
- Gunslinger: +2 Damage to pistols.
- Shredder: +33% Damage from all sources to the target.
- Flush: reduces damage by 50%.
- Disabling Shot: does 1/2/3 damage, depending on the Sniper Rifle's tech level.
- HEAT Ammo: +100% Damage against robotic enemies (has been lowered to 50% damage in the Enemy Within DLC).
- Mayhem: +1/2/3 Damage, depending on the weapon tech level to Suppression, +2 to Rocket Launcher and +3 to Blaster Launcher projectiles. Does not confer additional damage to grenades.
- Bring 'Em On: +1 to +5 bonus Critical Damage, depending on the number of enemies.
- Killer Instinct: +50% Critical Damage.
- Grenadier: adds +1 damage to Frag, Needle and Alien Grenades (EW DLC).
- Will to Survive: reduces incoming damage by 2, if in cover and not flanked.
- Mind Merge: when used upon a Mechtoid it will reduce all incoming damage by 50% as long as the shield is active (EW DLC).
- Reinforced Armor will reduce all incoming damage to a Sectopod by 50% (Enemy Within DLC).
- Shock-Absorbent Armor: Damage received from enemies within 4 tiles is reduced by 33%. (EW DLC).
- Collateral Damage: Area of effect attack that destroys most cover and hits all eligible targets for 34% damage. This attack cannot cause critical hits. Usually the damage inflicted will be 1/2/3, depending on the MEC Trooper's primary weapon. (EW DLC).
- Vital-Point Targeting: Confers 2 bonus damage against targets that have been autopsied. (EW DLC).
- Damage Control: When the MEC takes damage, all further damage will be reduced by 2 on the following 2 turns. (EW DLC).
- Absortion Fields: Any hit that makes 33% more damage to the MEC's maximum health is reduced to that number. (EW DLC).
- Improved Pistol III: All pistols Damage increased by 1 (EW DLC).
- Elerium Jelly: Increases Flamethrower damage from 6 to 9( EW DLC).
- MEC Close Combat: Increases Kinetic Strike Module's damage from 12 to 18 (EW DLC).
- Iron Skin: All damage taken is reduced by 25% (EW DLC).
Also, there seems to be a Damage cap (at least for explosives) - Rocket Launchers will deal 16 max damage using HEAT Ammo and Mayhem (on vanilla EU), regardless of using Shredder rockets or not.