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 talents, as well as some items. Most items in the armor shop provide armor bonuses.

Main armor
Main armor is the armor value shown in white numbers near 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:

.

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:

.

Armor granted by agility
The sum of agility points a hero has is multiplied by (1 / ) 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 abilities, items and talents.

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 unit's statistics. Whenever an item or skill shows a +armor value, e.g. (+5 Armor), it increases the bonus armor of the affected unit. Probably the most important 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. Some spells like also only affect main armor.

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.

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

For any real-valued armor, the damage multiplier is defined as



In Dota 2, the damage multiplier limits are 25/12 (roughly 2.08) and 0, for infinitely negative and positive armor, respectively.

 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" | %
 * align="center" | -1
 * align="right" | %
 * align="center" | 2
 * align="right" | %
 * align="center" | -2
 * align="right" | %
 * align="center" | 5
 * align="right" | %
 * align="center" | -5
 * align="right" | %
 * align="center" | 10
 * align="right" | %
 * align="center" | -10
 * align="right" | %
 * align="center" | 15
 * align="right" | %
 * align="center" | -15
 * align="right" | %
 * align="center" | 20
 * align="right" | %
 * align="center" | -20
 * align="right" | %
 * }
 * align="center" | 20
 * align="right" | %
 * align="center" | -20
 * align="right" | %
 * }
 * }

Effective health
The extra damage a unit can take due to armor is known as its extra effective health for physical damage. At 0 armor, 1 armor grants roughly 5.8% effective health. This means a unit with 1000 health and 1 armor can take 1058 physical damage. At 30 armor, this figure scales upwards to 7.7%, meaning armor is more effective at higher values.

On the other hand, the effectiveness of armor is much lower at negative values (see graph). Total effective health trends downwards towards 48%, meaning a unit with 1000 health and infinitely low armor would still be able to take 480 damage physical damage. At this point, losing or gaining 1 armor has essentially no effect.

This definition of effective HP assumes all damage taken is physical. In Dota 2, magical damage (such as 's or 's ultimate) is modified by magic resistance.

 Calculating effective HP: 

The formula to calculate the EHP is:

Method 1 (the definition above):

Method 2 (obtained by assuming the sign of the armor value and combining fractions):
 * If armor is positive,
 * If armor is negative,
 * If armor is negative,

Example 1:


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


 * By method 1, EHP = ÷ ( 1 - ( × ) ÷ (1 +  × ) ) =  ÷  =


 * By method 2, as his armor is positive, EHP = × (1 +  × ) =  ×  =


 * Sven can tank physical damage.

Example 2:


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


 * By method 1, EHP = ÷ ( 1 - ( × ) ÷ (1 +  × ) ) =  ÷  =


 * By method 2, as his armor is negative, EHP = × (1 -  × ) ÷ (1 - (2 ×  × )


 * Sven can tank physical damage.

Armor types
There are several different types of armor, which determine how much damage a unit takes against certain attack damage types. Each of the 3 different armor types either reduces, increases or does not affect the damage from each of the damage types, on top of armor values manipulating them.

Example:

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

This table shows how much damage each armor type reduces against each attack damage type and which unit uses which armor type (units which take a set amount of damage per attack are excluded).

Trivia

 * In DotA 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% or 65% . Nowdays in Dota 2 magic resistance works independently from armor.
 * The Basic armor type was refered to as Medium armor in DotA.
 * The deprecated Light damage type used to be called Chaos damage in DotA.
 * The deprecated Weak armor type used be called Light armor, Soft was referred to as Unarmored, and Strong was known as Heavy armor type.

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