Armor

Armor is an attribute shared by all units. Armor is used to determine the amount of damage reduction (or amplification if an armor value is negative) a unit takes from physical damage sources. Higher armor values reduce more damage. Armor is increased by Agility, certain abilities, and some items. Most items in the armor shop provide armor bonuses.

Main armor
Main armor is the armor value shown in white numbers below the shield icon in the HUD, consisting of base armor and the armor granted by a hero's agility. The only way to improve a hero's main armor is to increase its agility.

The formula to calculate a hero's main armor is:

main armor = base armor + (agility * 0.14).

Base armor
Base armor is the part of the main armor that never changes throughout a game. It consists of one fixed value set for each unit individually. The base armor of a unit can be a negative number. Since only heroes have agility, the HUD of all non-hero units shows their base armor.

The base armor of heroes can be calculated with this formula:

base armor = main armor - (agility * 0.14).

Armor granted by agility
The sum of agility points a hero has is multiplied by 0.14 and added on top of the base armor to define the main armor value. Agility can be increased by acquiring levels, as well as specific skills and items.

Bonus armor
Bonus armor is the armor value shown in green numbers with a plus on the left, right below the white armor number on a units's statistics. Whenever an item or skill shows a +armor value, eg Blade Mail (+6 Armor), it increases the bonus armor of the affected unit. The difference between main and bonus armor is that illusions only benefit from main armor, although their HUD still shows the bonus armor just like on other heroes, to make them less obvious to the enemy.

Armor increasing abilities
The following abilities are able to increase unit's armor:

Armor reducing abilities
The following abilities are able to reduce unit's armor:

Armor granting items
The following items increase a unit's Armor. The effects are limited to the item's owner, which must have the item equipped. (items in grey fields grant armor exclusively through agility gain)

Basic items

Upgraded items

Damage multiplier
All units, including buildings, have an inherent base armor value and armor type. Any physical damage dealt to a unit suffers either a damage reduction or a damage increase depending on the target's armor.

The damage multiplier for both positive and negative armor:


 * Damage multiplier = 1 - 0.06 armor  (1 + (0.06  |armor|))

In Dota 2, the cap on this number is 100% damage amplification or reduction, but it requires an infinite amount of negative or positive armor to truly reach these caps.

 Examples
 * {| class="wikitable" width = "480px"

! class = "header" width = "10%" align="center" | Armor ! class = "header" width = "40%" align="center" | Damage multiplier ! class = "header" width = "10%" align="center" | Armor ! class = "header" width = "40%" align="center" | Damage multiplier
 * align="center" | 1
 * align="right" | 94.3%
 * align="center" | -1
 * align="right" | 105.7%
 * align="center" | 2
 * align="right" | 89.3%
 * align="center" | -2
 * align="right" | 110.7%
 * align="center" | 5
 * align="right" | 76.9%
 * align="center" | -5
 * align="right" | 123.1%
 * align="center" | 10
 * align="right" | 62.5%
 * align="center" | -10
 * align="right" | 137.5%
 * align="center" | 15
 * align="right" | 52.6%
 * align="center" | -15
 * align="right" | 147.4%
 * align="center" | 20
 * align="right" | 45.5%
 * align="center" | -20
 * align="right" | 154.5%
 * }
 * align="center" | 20
 * align="right" | 45.5%
 * align="center" | -20
 * align="right" | 154.5%
 * }
 * }

Effective HP
It is useful to first understand the concept of effective HP. The damage reduction and increase percentage formulas are directly related to the effective HP formulas in the previous section. The amount of physical damage a unit can take before dying (hence likelihood of surviving) is not proportional to damage reduction percentages, but to effective HP. Effective HP is the amount of physical damage one can take before dying, and is based on the unit's HP.

For positive armor values, a unit gains 6% of their health per armor as effective HP. A hero with 0 armor and a base HP of 1000 increases his effective HP by 60% if he increases his armor to 10. For negative armor values, the effective HP reduction diminishes with decreasing armor, trending towards 0%.

One has to consider that effective HP only takes physical damage in consideration. The example assumes that all the damage the unit takes is physical. Armor actually grants 6% of the physical damage one takes. This becomes more evident with burst magical damage (such as Lina's or Lion's ultimate): the armor value in those cases count for nothing.

 Calculating effective HP: 


 * Effective HP = Total HP / Damage multiplier

Example 1:


 * A level 25 has a total HP of 2183 and 11.46 points of armor. What is his effective HP vs physical damage?


 * 2183 HP / ( 1 - (11.46 0.06) / (1 + 11.46  0.06) ) = 2183 HP / 0.5925 = 3684 effective HP


 * Sven can tank 3684 of physical damage before he dies.

Example 2:


 * The same Sven from previous example is hit by a maxed . His armor is now -8.54. What is his effective HP vs physical damage?


 * 2183 HP / ( 1 - (-8.54 0.06) / (1 + 8.54  0.06) ) = 2183 HP / 1.3388 = 1631 effective HP


 * Sven can tank 1631 of physical damage before he dies.

Armor types
There are now four different armor types that react diffently to each Damage type. They are called Soft, Basic/Strong, Fortified and the standard armor used by Heroes.

Effective physical damage by attack type and armor type

Trivia

 * In DotA 1 the base magic resistance was bound to the assigned armor. In case of Hero Armor only 75% of the magic damage was applied. Some heroes possessed hidden passive skills to alter their base magic susceptibility albeit Hero Armor to 90% (Visage) or 65% (Meepo). Nowdays in DotA 2 magic resistance works independently from armor.
 * The deprecated Light damage type used to be called Chaos damage in DotA 1.
 * Regarding armor in DotA 1, Weak was named Light, Soft was refered as Unarmored, Basic has been called Medium and Strong was known as Heavy.

Negative armor disparity
Amplified damage from negative armor is calculated differently in WC3 DotA than in Dota 2. .

Negative armor in WC3 DotA has a cap of -20 armor (71% damage increase). Further reducing the armor does not change the damage increase. . Also, the more aggressive damage amplify formula is used resulting in a max damage increase of 71 %. The amplified damage is calculated from this formula:


 * Damage increase = 1 - 0.94^(-armor)

 Comparison table 

Balance changelog

 * See Damage