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 will 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 show 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 and effective HP
It is useful to first understand the concept of effective HP. 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 will increase his effective HP by 60% if he increases his armor to 10.


 * 0 → 10 armor: 1000 → 1600 effective HP.


 * 0 → 20 armor: 1000 → 2200 effective HP.

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.

For negative armor values, the effective HP reduction diminishes with decreasing armor, trending towards 50%.

Calculating effective HP
For positive armor values:


 * Effective HP = Total HP (1 + Armor points  0.06)

Example:


 * 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) = 2183 HP  1.6876 = 3684 effective HP


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

For negative armor values:


 * Effective HP = Total HP (1 - 0.06  Armor points) / (1 - 0.12  Armor points)

Example:


 * 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 (1 - 0.06  -8.54) / (1 - 0.12  -8.54) = 2183 HP  1.51  2.02 =  1631 effective HP


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

Damage reduction/increase
The damage reduction and increase percentage formulas are directly related to the effective HP formulas in the previous section, and can be derived through algebra. All units, including buildings, have an inherent base armor value and armor type. Any physical damage dealt to a unit will suffer either damage reduction or a damage increase depending on the target's armor.


 * Damage reduction = (0.06 armor)  (1 + 0.06  armor)

Units with negative armor values increase any physical damage they receive.


 * Damage increase = (0.06 |armor|)  (1 + 0.06  |armor|)

Or, 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 amp, but it requires an infinite amount of negative armor to truly reach this cap.

This is different from WC3 DotA, where armor cannot be reduced below &minus;20. Also, a more aggressive damage amplify formula is used resulting in a max damage increase of 71 %. See Negative armor disparity for more information.

Damage multipliers at different armor values

 * {| 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" | -20
 * align="right" | 154.5%
 * align="center" | 1
 * align="right" | 94.3%
 * align="center" | -19
 * align="right" | 153.3%
 * align="center" | 2
 * align="right" | 89.3%
 * align="center" | -18
 * align="right" | 151.9%
 * align="center" | 3
 * align="right" | 84.7%
 * align="center" | -17
 * align="right" | 150.5%
 * align="center" | 4
 * align="right" | 80.6%
 * align="center" | -16
 * align="right" | 149.0%
 * align="center" | 5
 * align="right" | 76.9%
 * align="center" | -15
 * align="right" | 147.4%
 * align="center" | 6
 * align="right" | 73.5%
 * align="center" | -14
 * align="right" | 145.7%
 * align="center" | 7
 * align="right" | 70.4%
 * align="center" | -13
 * align="right" | 143.8%
 * align="center" | 8
 * align="right" | 67.6%
 * align="center" | -12
 * align="right" | 141.9%
 * align="center" | 9
 * align="right" | 64.9%
 * align="center" | -11
 * align="right" | 139.8%
 * align="center" | 10
 * align="right" | 62.5%
 * align="center" | -10
 * align="right" | 137.5%
 * align="center" | 11
 * align="right" | 60.2%
 * align="center" | -9
 * align="right" | 135.1%
 * align="center" | 12
 * align="right" | 58.1%
 * align="center" | -8
 * align="right" | 132.4%
 * align="center" | 13
 * align="right" | 56.2%
 * align="center" | -7
 * align="right" | 129.6%
 * align="center" | 14
 * align="right" | 54.3%
 * align="center" | -6
 * align="right" | 126.5%
 * align="center" | 15
 * align="right" | 52.6%
 * align="center" | -5
 * align="right" | 123.1%
 * align="center" | 16
 * align="right" | 51.0%
 * align="center" | -4
 * align="right" | 119.4%
 * align="center" | 17
 * align="right" | 49.5%
 * align="center" | -3
 * align="right" | 115.3%
 * align="center" | 18
 * align="right" | 48.1%
 * align="center" | -2
 * align="right" | 110.7%
 * align="center" | 19
 * align="right" | 46.7%
 * align="center" | -1
 * align="right" | 105.7%
 * align="center" | 20
 * align="right" | 45.5%
 * }
 * align="center" | -4
 * align="right" | 119.4%
 * align="center" | 17
 * align="right" | 49.5%
 * align="center" | -3
 * align="right" | 115.3%
 * align="center" | 18
 * align="right" | 48.1%
 * align="center" | -2
 * align="right" | 110.7%
 * align="center" | 19
 * align="right" | 46.7%
 * align="center" | -1
 * align="right" | 105.7%
 * align="center" | 20
 * align="right" | 45.5%
 * }
 * align="center" | 20
 * align="right" | 45.5%
 * }

Negative armor disparity
Amplified damage from negative armor is calculated differently in WC3 DotA than in Dota 2. In DotA the amplified damage is calculated from this formula:


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

Negative armor in DotA has a cap of -20 armor (71% damage increase). Further reducing the armor will not change the damage increase.

Armor types
Unit armor

Unit armor refers to the four basic armor types of most non-Hero units. Light armor is the default armor type of units. Unarmored and light units take 100% damage from all sources except piercing damage, which deals 200% to light armor and 150% to unarmored units. Medium armor takes reduced damage from piercing and siege damage, but increased normal damage. Heavy armor takes reduced damage from piercing damage, but increased damage from siege and normal damage.

(Actually, Heavy armor has no resistance benefits but it takes more damage from magical attacks. It is only called as Heavy Armor since most units have this armor property has high Armor values.)

Fortified armor

Fortified armor is the type used by buildings and some other units. It takes reduced damage from most sources and is one of the sturdiest types of armor, but takes increased damage from siege. Fortified armor has an innate 50% damage resistance to Heroes.

Hero armor

Hero armor is used by all Heroes in Dota 2. It provides increased resistance to most damage types, except other Heroes and Chaos. Hero armor has an innate 25% magic resistance with the exception of Visage, whose magic resist starts at 10% and is increased by levels in Gravekeeper's Cloak, and Meepo, with a base of 35%. This is calculated separately from armor.

Table of resistances
Notes:
 * 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.
 * This table is likely based on DotA 1 values and mechanics. It is yet to be confirmed officially if the different armor and damage types are still present, have undergone a rework or remained unchanged. So far either no intensive community testing has been performed or the results were not made public or the informations haven't found their way here yet.

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