Damage (LWR)

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Damage Calculation

Complete Damage Formula

Damage Taken = [((Weapon Damage + Barrel Modifiers) <-- Randomization ) * Target Modifiers] * [1 - Clamp((DR - Penetration) / 100, 0, 0.8)]

This can be broken down into 5 steps:

1) Weapon Damage = Weapon Damage

2) Barrel Damage = Weapon Damage + Barrel Modifiers

3) Travel Damage = Barrel Damage is Randomized (and for explosives fall off is then calculated)

4) Damage Dealt = Travel Damage * Target Modifiers

5) Damage Taken = Damage Dealt * [1 - Clamp((DR - Penetration) / 100, 0, 0.8)]

Each category represents a section of the damage calculation (as explained below).

Weapon Damage

This is simply the listed damage of each weapon (for XCOM) or base damage (for aliens). Alien weapon damage increases with alien level and leader upgrades.

Barrel Damage

Damage from the barrel is: Weapon Damage + Barrel Modifiers (e.g. Ranger, Alloy Enhanced Rounds, ...). It is truncated after each calculation. Some Barrel Modifiers give straight damage (e.g. +1 damage) and others give damage based on the weapon damage (e.g. +50% weapon damage). These are all summed together. For example, a sniper with Ranger (+1 damage), Magnum (+60% weapon damage), and a Sniper Rifle (6 weapon damage) would have a barrel damage of 6 + 1 + 3 = 10.

Almost anything that modifies Weapon Damage (e.g. +50% weapon damage) is added as a Barrel Modifier.

Barrel Damage can be viewed in-game by pressing F1.

Travel Damage

Travel Damage is basically the Barrel Damage that is modified by Randomization.

For all damage 1-9, the damage is randomized from -1 to +1, with an even chance of being -1, 0, or +1 (the minimum damage is always at least 1). For all damage 10-19, the damage is randomized from -2 to +2, with an even chance of being -2, -1, 0, +1, or +2. The same occurs for damage of 20-29, 30-39, etc.

The actual formula is: Randomized Damage = Max(1, Damage + Rand[1 + (2 * (1 + Damage / 10))] - (1 + Damage / 10)). The randomization works in integer values so all values are constantly truncated (e.g. If x is 6 then x/10 = 0).

If this is a critical hit (from an explosive or a shot), any damage that would be randomized lower than the Barrel Damage is instead set to the Barrel Damage.

Randomization can occur twice or not at all if certain second wave options are enabled.

Damage Dealt

Once it reaches the targets, Target Modifiers are applied. The first target modifier applied is critical damage. If the shot or explosive rolled a critical hit, the damage is increased by 50%. Other target modifiers also applied include: Shred, VPT, CST, Graze, Distortion, TK Field, Brawler. After each calculation the damage is truncated to an integer.

Critical Damage has a base of 150% (so it adds 50% to the damage dealt). However, many abilities can increase this to higher levels.

Damage Dealt cannot be lower than 1.

Damage Taken

Damage Taken = Damage Dealt * (1 - (DR - Pen) / 100))

Note that the final result from the (DR - Pen) step has a cap of 80%. This is to prevent units from becoming nigh unkillable. Do note that extra DR can still be useful for counteracting pen while remaining at 80% DR.

The Damage Taken is truncated only after all DR has been removed from the Damage Dealt. Damage Dealt cannot be reduced below 1 by Damage Resistance. Penetration cannot reduce DR below 0.

To calculate total %DR, see Base DR.

Exceptions

Mins and Maxes

The Damage Taken cannot be reduced below 1 by Damage Resistance.

Randomization will never set the damage below 1.

Truncation

All damage is stored in an integer form, thus it is always being truncated during each step. This means 5.6 becomes 5, 9.1 becomes 9, and 9.9 becomes 9.

The exception to this is that Damage Resistance is not truncated and is removed from damage after calculation.

So Damage Dealt is truncated only after all DR is removed.

This is important, because having DR NOT truncated until it's removed from the Damage Dealt means that you can have small amounts of DR (i.e. 2% DR) be effective.

Explosive Damage

Each unit damaged by explosive damage has the Travel Damage reduced based on distance from the center after it is randomized. Damage falls off linearly to 35% at the periphery. The exception to this is that damage within 1 tile of the center has no fall-off.

Note: +0.5 damage is added on explosive fall-off to accommodate for truncation.

Special Damage Types

Psi Damage have their own methods of determine damage and are not affected by Target Modifiers or Damage Resistance.

Example Calculations

Mental In-Game Calculation

A soldier with a 3 damage Assault Carbine and Ranger (+1 damage) fires at a drone who has 50% DR.

You'd expect it to do 4 damage (range 3-5), minus 50% DR down to 2 damage.

Detailed Calculation

A soldier with an Assault Rifle and the Ranger perk fires at a Drone

The Assault Rifle has 4 Weapon Damage, receives +1 damage as a Barrel Modifier from Ranger, and has no innate Penetration.

The Drone is Hardened (30% DR) and has 20 base DR. The Total DR is 30 + 20 = 50%.

There are no Target Modifiers to the damage.

The shot does not 'Crit' so Crit Dmg is 1.0 and the Randomization does not change the value.

Damage Dealt = [((Weapon Damage + Barrel Modifiers) <-- Randomization ) * Target Modifiers] * (1 - (Total DR - Penetration) / 100)

Damage Dealt = [((4 + 1) + 0) * 1.0] * (1 - (50 - 0) / 100) = 2.5 = 2 Damage Taken

Environmental Damage

Environmental damage is the damage done to objects and structures around the battlefield (like walls, chairs, cars, etc.).

Each weapon has a specific environmental damage based on its size and type:

Weapon Type	Environmental Damage
Shots	15
Explosives	35

Environmental damage is mostly unaffected by perks and abilities and just considers the weapon's specific environmental damage. However, there are 2 exceptions: Explosives do tapper their environmental damage down to 35% at their periphery (and Tandem Warheads does prevent this tapper) and Sapper increases environmental damage.

Fire will also cause a lot of environmental damage and can spread. Be careful taking cover behind objects that are on fire!

All objects have a certain amount of HP. The less sturdy the object the less HP it will have. When an object's HP is reduced to 0 or less it will crumple.

Most cover has between 30 and 90 HP, based on what they are made of -- stone is tougher than wood, for example. Some map elements are entirely invulnerable and non-cover objects usually have less than 30 HP. Meld Canisters have 3 HP. Vehicles take 250 before catching on fire and 500 will cause them to explode immediately. Examples of the HP of objects can be found in the pictures below.