Armor

Armor is an attribute shared by all units. It reduces the amount of physical damage a unit takes, but can also increase the amount of damage if it's negative. 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.

Damage reduction/increase

Damage multiplier based on hero's armor rating

Damage reduction is derivative of a unit's armor value. 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)) × 100

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

Damage increase = 1 − 0.94^−armor

Armor cannot be reduced below −20 (71% damage increase). Further reducing the armor will not change the damage increase.

	Armor	Damage reduction (%)		Armor	Damage amplification (%)
	1	5.7		-1	6.0
	2	10.7		-2	11.6
	3	15.3		-3	16.9
	4	19.4		-4	21.9
	5	23.1		-5	26.6
	6	26.5		-6	31.0
	7	29.6		-7	35.2
	8	32.4		-8	39.0
	9	35.1		-9	42.7
	10	37.5		-10	46.1
	11	39.8		-11	49.4
	12	41.9		-12	52.4
	13	43.8		-13	55.3
	14	45.7		-14	57.9
	15	47.4		-15	60.5
	16	49.0		-16	62.8
	17	50.5		-17	65.1
	18	51.9		-18	67.2
	19	53.3		-19	69.1
	20	54.5		-20	71.0
	21	55.8		-21	71.0
	22	56.9		-22	71.0
	23	58.0		-23	71.0
	24	59.0		-24	71.0
	25	60.0		-25	71.0

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.

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, though this is calculated separately from armor.

Table of resistances

Damage Type	Armor Type
	Unarmored	Light	Medium	Heavy	Fortified	Hero
Normal	100%	100%	150%	125%	70%	75%
Pierce	150%	200%	75%	75%	35%	50%
Siege	100%	100%	50%	125%	150%	75%
Chaos	100%	100%	100%	100%	40%	100%
Hero	100%	100%	100%	100%	50%	100%
Magic	100%	100%	100%	100%	100%	75%

Armor stacking

Armor value stacks with multiple instances of items and abilities. Every point of armor requires a Hero to take 6% more of their maximum hit points in damage to kill. This is called "effective hit points", or EHP. A Hero with 10 armor has 160% of their maximum hit points as EHP, meaning that if a Hero had 1000 hit points, it would take 1600 points of physical damage to kill them. If that Hero had 20 armor, he or she would take 2200 points of physical damage to kill, doubling their protection.

Note, damage reduction does not stack directly.

List of items and abilities that grant armor

Armlet of Mordiggian 2600 Armor: 5	Assault Cuirass - Assault Aura 5350 Armor: 5 Radius: 900
Assault Cuirass 5350 Armor: 10	Axe - Berserker's Call Armor: 40 Duration: 1.5/2/2.5/3
Blade Mail 2200 Armor: 6	Bloodseeker - Thirst Armor: 3/4/5/6
Dragonspawn Camp - Blue Dragonspawn Overseer - Guardian Aura Armor: 3 Radius: 900	Buckler - Armor Bonus 803 Armor: 2 Radius: 750 Duration: 25 (Heroes) 30 (Units)
Buckler 803 Armor: 5	Chainmail 550 Armor: 5
Dazzle - Weave Armor: 1 per second Radius: 575(775*) Duration: 12/18/24 (18/24/30*)	Dragon Knight - Dragon Blood Armor: 3/6/9/12
Helm of Iron Will 950 Armor: 5	Helm of the Dominator 1850 Armor: 5
Lich - Frost Armor Armor: 3/5/7/9 Duration: 40	Lone Druid - Battle Cry Armor: 2/4/6 Duration: 8
Lone Druid - True Form Armor: 4/6/8	Lycanthrope - Shapeshift Armor: 1 Duration: 18
Medallion of Courage 1075 Armor: 6	Mekansm 2306 Armor: 5
Mekansm - Restore 2306 Armor: 2 Radius: 750 Duration: 25	Platemail 1400 Armor: 10
Ogre Camp - Ogre Frostmage - Ice Armor Armor: 8 Duration: 45	Ring of Aquila - Aquila Aura 985 Armor: 2 Radius: 900
Ring of Aquila 985 Armor: 1	Ring of Basilius - Basilius Aura 500 Armor: 2 Radius: 900
Ring of Basilius 500 Armor: 1	Ring of Protection 175 Armor: 2
Satanic 6150 Armor: 5	Shiva's Guard 4700 Armor: 15
Sven - Warcry Armor: 4/8/12/16 Radius: 900 Duration: 7	Timbersaw - Reactive Armor Armor: 1 Armor per stack, maximum of 4/8/12/16 stacks. Duration: 16
Tiny - Craggy Exterior Armor: 2/3/4/5	Tranquil Boots 975 Armor: 3
Troll Warlord - Berserker's Rage Armor: 3	Veil of Discord 2650 Armor: 6
Visage - Gravekeeper's Cloak Armor: 1/2/4/5 per layer, maximum of 4 layers.	Vladmir's Offering - Vladmir's Aura 2050 Armor: 5 Radius: 900
Wildwing Camp - Wildwing Ripper - Toughness Aura Armor: 3 Radius: 900

List of items and abilities that reduce armor

Alchemist - Acid Spray Armor Reduction: 3/4/5/6 Radius: 625	Assault Cuirass - Assault Aura 5350 Armor Reduction: 5 Radius: 900
Bristleback - Viscous Nasal Goo Armor Reduction: 1/1/2/2 per stack, maximum of 4 stacks. Duration: 5	Dazzle - Weave Armor Reduction: 1 per second Radius: 575(775*) Duration: 12/18/24 (18/24/30*)
Desolator - Corruption 4100 Armor Reduction: 7 Duration: 15	Elder Titan - Natural Order Armor Reduction: 25%/50%/75%/100% Radius: 275 Armor reduction only applies to base Armor and Armor gained via Agility.
Invoker - Forged Spirit - Melting Strike Armor Reduction per hit: 1 Maximum Armor Reduction: 10 Duration: 5	Medallion of Courage - Valor 1075 Armor Reduction: 6 Duration: 7 Affects both user and target.
Naga Siren - Rip Tide Armor Reduction: 2/3/4/5 Duration: 8	Razor - Eye of the Storm Armor Reduction per Strike: 1 Duration: 30
Shadow Fiend - Presence of the Dark Lord Armor Reduction: 3/4/5/6 Radius: 900	Slardar - Amplify Damage Armor Reduction: 8/14/20 Duration: 25
Templar Assassin - Meld Armor Reduction: 2/4/6/8 Duration: 10	Tidehunter - Gush Armor Reduction: 2/3/4/5 Duration: 4
Vengeful Spirit - Wave of Terror Armor Reduction: 2/3/4/5 Duration: 20	Weaver - The Swarm Armor Reduction per Attack: 1

See Also

• Magic resistance
• Agility
• Damage types
• Armor (Shop)