Attack damage

Attack damage is the amount of damage a unit is shown to deal with a regular attack. A unit's total attack damage is the sum of its main attack damage (white) and bonus attack damage (green). Attack damage is modified by many different effects in the game and ends up going through a number of steps in order to determine how much damage an attack actually deals as its overall or total attack damage.

Total Attack Damage
Calculating the total damage of an attack involves using many different multipliers and values. Total attack damage is synonymous with how much health a target immediately loses as a direct result of the attack. Some on-hit effects that are not affected by critical strike are still considered part of attack damage, and some are not.

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Formula:

Base attack damage
Base attack damage is the part of the main attack damage that stays the same throughout a game. It consists of two values, a minimum and maximum amount. Every time an attack is issued, a random value between these two extremes is chosen to help decide the damage output. The most extreme hero example of this is Chaos Knight, with base attack damage ranging between 29 and 59, causing his damage output to be somewhat unpredictable (or at least much less predictable than other heroes). This range of 30 is always part of his attack calculations, no matter how many attributes or how much bonus attack damage he acquires.

Main attack damage
Main attack damage is the damage value shown in white numbers on a hero's statistics consisting of the base attack damage with the damage granted by a hero's primary attribute on top. A hero's main attack damage can only be increased by raising its primary attribute, or by very few specific abilities. Attribute points can be acquired by leveling up, or by using specific items, abilities, or talents that raise attributes.

Formula:

Bonus attack damage
Bonus attack damage comprises the green number next to main attack damage. It comes in two types:
 * Flat Bonus: adds a flat number of damage to the unit's damage total. Examples:, ,
 * Percentage Bonus: adds an amount of bonus attack damage equal to a percentage of the affected unit's main attack damage, or total attack damage, depending on the ability. Examples: ,
 * While bonus attack damage is usually positive, it can also use a negative value, serving to reduce a unit's net attack damage. Examples:, ,

Formula

Critical strike multiplier
Critical Strike is an attack modifier that multiplies the total attack damage certain factor. If an attack activates more than one critical strike, only the highest multiplier is applied.

Blocked damage
Damage Block is a passive ability that gives the unit a chance to block a certain number of physical damage from an attack. If an attack activates more than one damage block ability, only the highest block value is applied.

Armor value multiplier
The target's armor influences the attack damage by a factor that asymptotically lies between 0 and 2 and is 1 for a target that has no armor.

Defense class multiplier
Depending on the combination of the attack class and defense class, an defense class multiplier modulates the attack damage.

General damage multipliers
A few abilities such as and  modify all incoming damage, including attack damage. reduces attack damage specifically.

Attack Classes
There are several different classes of attack damage (also known as Attack types or attack damage types), which determine how much damage a unit's attack deals against certain defense classes. Each of the 4 different attack classes deals either reduced, increased, or unchanged damage against each of the defense classes, on top of it being also manipulated by the armor value of the target.

Example A hero with 100 attack damage attacking a siege unit which has 0 armor deals 50 damage to it, because the attack class "hero" deals 50% less damage against the defense class "structure", which is the siege creeps' and all buildings' defense class. If the siege creep would gain 5 armor, the 100 damage attack would deal (100 * 0.8 * 0.5) = 40 damage. The same attack would deal 80 damage to a unit with any other defense class, since attack class hero deals full damage to them.

This table shows how much damage each attack class deals against each defense class, and which units use which attack class:

Instant Attacks
Instant Attacks are abilities that make use of the hero's regular attacks and dealing instant damage to the target unit(s) or area. Instant Attacks do not use the hero's attack animation, are independent from attack speed, and ignores the regular downtime between attacks. Certain abilities that deal instant attack damage are not affected by evasion. If an instant attack is performed by a ranged hero, it still uses their regular attack projectile for the attack, unless it is set not to.

If an instant attack occurs while already attacking an enemy normally, it does not interfere with the regular attack. They do not interfere with any other actions of the hero either, meaning they do not interrupt movement, do not cancel spell casts and do not stop channeling spells of the hero.

Since instant attacks do not use attack animations and jump straight to the attack point, they cannot proc effects which react on the start of an attack, like or. However, they can proc effects which react on attack hit, such as and, although there are some exceptions to this. Instant attacks may proc on-hit effects only when they are allowed to. An instant attack which is not allowed to proc attack modifiers is not allowed to proc on-hit effects either. Just like regular attacks, instant attacks also cause the attacking hero to get revealed if attacking from the Fog of War.

The following abilities make use of instant attacks:

1 Requires talent.

2 Requires.

3 Grants instant attacks to tier 2, 3, and 4 towers.

4 These instant attacks may not proc any attack modifiers or on-hit effects.

5 Split Shot may not proc any attack modifiers or on-hit effects, unless the required talent is chosen.

6 Number of instant attacks is dependent on Juggernaut's attack speed.

Percentage Bonus

 * Gives a unit a damage buff equal to a percentage of their main attack damage.

Conditional bonus
These abilities give direct attack damage bonuses under certain circumstances. Due to this, they do not display their damage bonus in the HUD. Their damage type can also vary and is not necessarily physical; nonetheless, they still count as attack damage since their damage is dealt in one instance together with a unit's attack damage. This means they are affected by defense class (even when dealing magical damage), but not by spell damage amplification.

Percentage reduction

 * Main attack damage reduction applies to main attack (white damage) only.
 * Overall attack damage reduction applies to both main attack damage (white) and bonus damage (green).
 * All effects shown here reduce the affected unit's damage before any damage block is applied.

Flat reduction
Flat damage reduction is applied before crits as negative bonus attack damage.

Conditional reduction
These abilities reduce attack damage under certain circumstances. Due to this, they do not display their reductions in the HUD.