Use your favourite features in-game with our Desktop AppArmour is one of the standard Defence stats in Path of Exile 2. You'll typically find Armour related stats on Strength-aligned gear and on the left side of the passive skill tree.
Tip: check out our guide on the other standard Defence stats: Energy Shield and Evasion!
Armour is a defensive stat that mitigates Physical Hit Damage by default. The Physical Damage Reduction provided by Armour is not static, and instead varies based on the size of the Hit taken vs total Armour. By design, Armour is stronger against many small Hits rather than few large Hits, even if the total combined Damage of those Hits are equal.
Damage mitigated by Physical Damage Reduction counts as prevented Damage for mechanics such as 
Made to Last.
Armour does not interact with Damage over time in any way and will not mitigate the Physical Damage over time from Bleeding or Corrupted Blood.
Tip: see the section on Additional Physical Damage Reduction below!
The formula below is used to calculate the Damage Reduction provided by Armour, where AR is the total Armour value of the defender and DMG is the total Physical Damage in the Hit taken by the defender.
Armour can mitigate Physical Damage up to a fifth of its total value. For example a character with 20,000 Armour is able to mitigate up to 4000 Physical Damage from a single Hit with the Damage Reduction provided by Armour alone. However, at the opposite end of the scale when the Physical Damage in a Hit largely exceeds the total Armour value, Armour will not mitigate more than a tenth of its value in Damage at its minimum level of mitigation.
The following list provides some examples of the Damage Reduction provided by Armour at given levels of Armour vs Hit Damage:
Physical Damage Reduction is hard-capped at 90% from all sources, including Armour.
Additional Physical Damage Reduction, also known as PDR, is a modifier that provides a static percentage of Physical Damage Reduction. Multiple sources of Additional Physical Damage Reduction stack additively with each other.
The Physical Damage Reduction provided by these modifiers is added directly to the percentage of Damage Reduction from the above Armour calculation before being applied. For example a character has '8% Additional Physical Damage Reduction' from their equipped Shield and they have 10,000 total Armour. The character takes a Hit of 1000 Physical Damage. Armour alone would mitigate 50% of the Damage, and therefore the character mitigates 58% of the Damage of that Hit after the Additional Physical Damage Reduction modifier has been factored in.
Unlike Armour, modifiers that provide Additional Physical Damage Reduction will apply mitigation to any Physical Damage over time, such as the Damage from Bleeding or Corrupted Blood.
Armour Break is an offensive mechanic that temporarily removes a flat amount of Armour from the target, for a default base Duration of 12 seconds. Armour is Fully Broken once enough Armour is removed to bring the target's Armour value to zero. Armour will remain Fully Broken for 12 seconds, or until it's consumed by a Skill.
Note: Monsters can possess Armour Break abilities or global Armour Break modifiers which can be dangerous for Armour-based characters!
Applying Armour Break to Monsters will break 3 times as much Armour against Normal Monsters and twice as much against Magic Monsters.
The Warbringer's 
Imploding Impacts will allow the character to break the Armour of Monsters beyond zero, into the negatives. Negative Armour is capped at an inverse amount compared to the original total Armour value of the Monster. For example a Monster with 2000 Armour could have their Armour reduced to -2000. Negative Armour will cause Physical Damage Hits against the target to gain a Damage multiplier rather than a reduction at the same ratio.
Overwhelm is an offensive mechanic that makes the Physical Damage in a Hit bypass a stated amount of the defender's Physical Damage Reduction. These modifiers can apply globally to all of the Hits an entity performs, or be tied to specific abilities.
For example the Pinnacle Breach Boss Xesht, We Who Are One has the Sonic Wave Finger Gun ability that deals pure Physical Hit Damage and has the modifier 'Overwhelm 30% Physical Damage Reduction'. The Damage dealt by this ability will be calculated using the Armour formula above, including any Additional Physical Damage Reduction that the defender has. The defender's Physical Damage Reduction to the Hit will then effectively be lowered by the stated amount of Overwhelm against the Damage of that Hit.
Note: Overwhelm cannot bypass Physical Damage Reduction beyond 0%.
Armour is primarily gained from gear: Helmets, Body Armours, Gloves, Boots and Shields. The majority of the Strength-aligned base types have inherent Armour present as the Defence stat that's tied to the item. This portion of Armour can be scaled by local modifiers, for example 'X% increased Armour' or '+X to Armour'. These local modifiers scale the Armour gained from the piece of gear directly and do not apply globally to your character. The Quality stat is a multiplier on the final amount of Armour on a piece of gear.
A local modifier is one that only applies to a stat on the item it's present on, whilst a global modifier will apply to the total stat on the character. Local modifiers are found on items with inherent stats, for example Gloves with inherent Armour will be able to roll local modifiers that improve the inherent Armour on the item. However on items where there is no inherent stat such as Jewels, or on items that can roll modifiers that do not apply to the inherent stat, such modifiers are typically global modifiers.
For example the Amulet below has a modifier that grants '34% Increased Armour' which is applied globally to the character's flat Armour, as it cannot apply locally to any stat on the item.
The Body Armour below has '28% Increased Armour' in addition to '+54 to Armour'. However, as this item has inherent Armour, these modifiers are applied locally to increase the total flat Armour gained from the item.
Flat Armour gained from equipment or other sources is added together and scaled by any global Armour modifiers you have, such as 'X% increased Armour' from the passive skill tree.
Note: modifiers to Global Defences will also scale Armour.
Some modifiers will multiply your Armour value for the purpose of defending against a Hit under specific conditions. For example Blade Catcher has the modifier 'Defend with 200% of Armour against Critical Hits', essentially doubling your total Armour for the purpose of mitigating incoming Critical Hits.
The 
Iron Reflexes Keystone converts all of your character's Evasion Rating into Armour. Only modifiers that scale Armour will apply to the converted portion of Armour; modifiers that scale Evasion Rating will no longer apply to this stat.
There are some rare modifiers that will apply Armour to non-Physical Damage types. For example, the Heatproofing Passive tree notable applies a quarter of your Armour to Fire Damage taken from Hits. When Armour is applied to non-Physical Damage, it's Damage Reduction is calculated and applied prior to the mitigation from Resistances.
The 
Blackbraid Unique Body Armour makes your Armour apply to all Fire, Cold and Lightning Damage Hits in addition to the standard Physical Damage. When Armour is applied to multiple Damage types in the same Hit, the Damage Reduction calculation is applied separately to each Damage type.
