Armour

For equipment classified as armour, see Equipment.

Armour is a rating that measures a character's physical damage mitigation.

Armour rating can be increased by wearing equipment, taking certain passive skills, using spells such as Molten Shell, and drinking Granite Flasks.

Supposedly the most armour monsters have in the game is about 930 .

Mechanics

Damage reduction from armour only reduces physical damage taken. Elemental damage and damage-over-time are not affected.

The amount of damage reduction is a function of armour rating and the damage taken. Damage reduction is capped at 90%.

Damage Reduction Factor = Armour / ( Armour + (12 * Damage) )

For example, if you have 1200 armour rating this chart indicates how much damage will be reduced by:

File:Damage reduction chart.png The vertical axis is damage reduction percent. The bottom axis is original damage.

Equivalently:

Net Damage = Raw Damage2 / (Raw Damage + Armour / 12)
Defense Factor = Raw Damage / Net Damage = 1 + Armour / (12 * Raw Damage) 
= (1 + sqrt(1 + Armour / (Net Damage * 3))) / 2

Therefore we can conclude:

• If raw damage is much less than Armour / 12, raw damage has a near-quadratic effect on net damage. Equivalently, in this regime raw damage has a near-linear effect on net DPS if the raw DPS is held constant.
• If raw damage is much greater than Armour / 12, raw damage has a near-linear effect on net damage. Equivalently, in this regime raw damage has little effect on net DPS if the raw DPS is held constant.
• Against attacks of a fixed raw damage, armour has a linear effect on the number of attacks it takes to deplete a certain amount of hit points.

Another way of looking at it is in terms of absolute damage reduction:

Absolute damage reduction = Armour / 12 * Raw Damage / (Raw Damage + Armour / 12)

So damage from attacks is reduced by up to 1 per 12 points of Armour, which means that the supposed monster Armour cap of 930 blocks up to 77.5 damage per attack. Note that as raw damage increases, the damage blocked per attack increases, but the proportion of damage blocked decreases.

Passives

There are passive skill nodes that grant additional evasion or a combination of bonuses including evasion.

Armour

These passives increase armour rating by a percentage.

In the case of Iron Reflexes, armour is increased by an amount equal to total evasion. In exchange, evasion is reduced to 0.

Icon	Name	Bonuses
File:Passive-armour.png	Armour	10% increased Armour 12% increased Armour 15% increased Armour
File:Passive-steelskin.png	Steel Skin	30% increased Armour
File:Passive-armourmastery.png	Armour Mastery	18% increased Armour 2% increased Movement Speed
File:Passive-armourandevasion.png	Armour and Evasion	8% increased Evasion Rating and Armour
File:Passive-leatherandsteel.png	Leather and Steel	24% increased Evasion Rating and Armour Ignore all movement penalties from Armour
File:Passive-armourandenergyshield.png	Armour and Energy Shield	8% increased Armour 6% increased maximum Energy Shield
File:Passive-bodyandsoul.png	Body and Soul	20% increased Armour 20% increased maximum Energy Shield +10% to all Elemental Resistances
File:Passive-keystone-ironreflexes.png	Iron Reflexes	Converts all Evasion Rating to Armour

Miscellany

These passives are related to armour, but don't fit into any other category.

Icon	Name	Bonuses
File:Passive-keystone-acrobatics.png	Acrobatics	20% chance to Dodge Attacks Removes all Armour and Energy Shield