Armor is the defensive stat that reduces incoming physical damage by a percentage. 100 armor cuts physical damage in half. 200 armor reduces it by 66.6%. Every point of armor increases your effective health against physical damage by 1%, and armor multiplies with HP so that each additional point remains equally valuable regardless of how much you already have. When the enemy team has two or more primary AD threats, one armor item can swing fights that are otherwise losing. The counter to armor is lethality and percent armor penetration. Item picks and strategy for AD players below.
How Armor Works
The damage formula is: post-mitigation damage = raw physical damage × 100 / (100 + armor).
At 100 armor, an ability dealing 1,000 raw physical damage hits for 500. At 200 armor, that same ability hits for 333. The percentage reduction formula is armor / (100 + armor). At 100 armor that is 100 / 200 = 50%. At 200 armor it is 200 / 300 = 66.6%.
Armor stacks additively. A 75 armor item and a 50 armor item together give 125 armor with no interaction penalty. There are no diminishing returns. Each additional point of armor adds 1% more to your effective health pool against physical damage regardless of how much you already have. 300 armor is four times as effective as 30 armor, not three times.
Armor and HP multiply each other for effective health. A champion with 2,000 HP and 100 armor has 4,000 effective HP against physical damage. Adding a second 100 armor (going to 200) raises that to 6,000 effective HP. Adding HP to a high-armor champion and armor to a high-HP champion both produce larger absolute gains than adding more of what you already have. That multiplicative interaction is why most armor items include HP.
Lethality reduces the effective armor the attacker uses in the damage calculation, not your actual stat. 30 lethality means the attacker treats your armor as 30 lower. Your item stats and any other effects relying on your actual armor still see the full value.
Armor vs. Physical Damage: Damage Table
The table below shows what percentage of physical damage gets through at each armor level. Lower percentages mean less damage received.
| Armor | No Pen | 30 Lethality | 35% Armor Pen (Lord Dominik's Regards) |
|---|---|---|---|
| 0 | 100.0% | 100.0% | 100.0% |
| 30 | 76.9% | 100.0% | 83.7% |
| 50 | 66.7% | 83.3% | 75.5% |
| 100 | 50.0% | 58.8% | 60.6% |
| 150 | 40.0% | 45.5% | 50.6% |
| 200 | 33.3% | 37.0% | 43.5% |
| 250 | 28.6% | 31.2% | 38.1% |
| 300 | 25.0% | 27.0% | 33.9% |
At 30 armor (roughly what a mage has with no armor items), 30 lethality erases it entirely and the attacker deals full unmitigated damage. At 100 armor (a bruiser with one armor item), the same 30 lethality closes the gap from 50% to 58.8%: meaningful but far from full penetration. At 300 armor, lethality barely moves the needle. Percent penetration scales with the target's armor and keeps closing the gap at high armor values where lethality becomes negligible.
The crossover between lethality and percent penetration falls around 100 to 150 armor. Below that, lethality is more efficient. Above it, Lord Dominik's Regards pulls ahead.
Armor vs. Health
Health and armor both increase effective health against physical damage, but in different ways. Health is universal: it increases your buffer against physical damage, magic damage, and true damage equally. Armor only helps against physical sources.
The two stats multiply together, which means you get the most out of each by building both. A useful rule of thumb: each point of armor is worth roughly the same effective HP as one point of health, so the most efficient build keeps the two roughly balanced rather than stacking one to the exclusion of the other. A champion with 200 armor and 800 HP is far less durable than the same gold split between 100 armor and 1,800 HP, because the armor without the HP to multiply against has nowhere to compound. Most armor items include HP for exactly this reason.
Unlike MR, armor applies to basic attack damage as well as physical abilities. Champions who primarily deal auto-attack damage (ADCs, on-hit fighters) are hard-countered by heavy armor stacking in ways that pure AP mages rarely are against a single MR item. Frozen Heart's attack speed reduction compounds this: it reduces both the frequency and the effectiveness of physical basic attacks simultaneously.
All Armor Items (2026)
| Item | Gold | Armor | HP | Other Stats | Role |
|---|---|---|---|---|---|
| Thornmail | 2,450 | 75 | 150 | - | Tank |
| Frozen Heart | 2,500 | 75 | - | 20 Ability Haste, 400 Mana | Tank / Bruiser |
| Randuin's Omen | 2,700 | 75 | 350 | - | Tank |
| Dead Man's Plate | 2,900 | 55 | 350 | 4 Move Speed | Tank / Bruiser |
| Sunfire Aegis | 2,700 | 50 | 350 | 10 Ability Haste | Tank |
| Unending Despair | 2,800 | 50 | 400 | 15 Ability Haste | Tank |
| Iceborn Gauntlet | 2,900 | 50 | 300 | 15 Ability Haste | Bruiser / Tank |
| Death's Dance | 3,300 | 50 | - | 15 Ability Haste, 60 AD | Bruiser |
| Guardian Angel | 3,200 | 45 | - | 55 AD | Bruiser / ADC |
| Jak'Sho, The Protean | 3,200 | 45 | 350 | 45 Magic Resist | Tank |
| Warden's Mail | 1,000 | 40 | - | - | Tank / Bruiser |
| Knight's Vow | 2,300 | 40 | 200 | 10 Ability Haste, 100 Percent Base Health Regen | Support / Tank |
| Bramble Vest | 800 | 30 | - | - | Tank |
| Plated Steelcaps | 1,200 | 25 | - | 45 Move Speed | All |
Armor values from patch 16.9.1.
What distinguishes each item beyond its armor value:
- Thornmail — Bramble Vest at full item scale; returns damage and applies Grievous Wounds when hit
- Frozen Heart — reduces attack speed of nearby enemies by 20%; best against auto-attack-heavy compositions
- Randuin's Omen — reduces incoming critical strike damage by 30%; active slows nearby enemies
- Dead Man's Plate — momentum stacking grants move speed; empowers the next basic attack on engagement
- Sunfire Aegis — Immolate passive deals AoE magic damage to nearby enemies; engagement tank
- Unending Despair — passive drains HP from nearby enemies when on low health; sustain for frontline tanks
- Iceborn Gauntlet — spellblade creates a slowing zone on the next basic attack after an ability cast
- Death's Dance — converts 30% incoming damage to a bleed over 3s; cleanse on champion takedown
- Guardian Angel — revive passive triggers once per death; standard late-game bruiser and ADC defensive item
- Jak'Sho, The Protean — stacks bonus armor and MR mid-fight; ideal against mixed AD and AP compositions
- Warden's Mail — reduces attack speed of nearby enemies by 15%; component for Thornmail, Frozen Heart, Randuin's Omen
- Knight's Vow — support bond: redirects 12% damage from bonded ally to you while near them
- Bramble Vest — returns damage and applies Grievous Wounds when hit by basic attacks; early counter to lifesteal
- Plated Steelcaps — boots; also reduces all incoming basic attack damage by 10%
When to Build Armor
Build armor when two or more enemy champions deal primary physical damage: an ADC in the bot lane, an AD assassin or bruiser in the jungle or mid, especially if one of them spikes hard with a lethality item. The practical trigger: if the enemy team has at least two AD-primary champions, buy your first armor item before or during your second item slot.
One cheap armor item early outperforms a gold-equivalent amount of HP against a lethality spike. Going from 30 armor (base) to 55 armor with a 300g Cloth Armor component reduces the assassin's physical damage against you by roughly 15%. That same Cloth Armor when you already have 200 armor reduces damage by under 2%. Front-load armor investment against lethality champions who spike in the mid-game.
Role-based armor targets:
- Tank / engage support: Target 150 or more total armor against a heavy AD comp. Thornmail is the best first buy when the enemy has heavy lifesteal (Kog'Maw, Samira, healing-reliant bruisers) because the Grievous Wounds application happens automatically on being hit. Frozen Heart is stronger against high attack speed ADCs (Jinx, Kog'Maw, Tristana) because the 20% attack speed reduction multiplies with your armor to reduce incoming DPS by more than either stat alone. Randuin's Omen is the right pick against crit-heavy compositions (Infinity Edge Jinx or Caitlyn) because the 30% crit damage reduction stacks with your armor reduction to cut burst.
- Top or jungle bruiser: Dead Man's Plate is the standard first armor buy for roaming bruisers; the momentum passive provides both a move speed bonus and a damage spike on engagement. Iceborn Gauntlet suits ability-casting bruisers (Garen, Malphite) who apply the spellblade slowing zone repeatedly. Death's Dance is the right pick when you want to survive burst without going full tank: the 30% damage conversion gives you time to heal or escape before the bleed kills you.
- ADC: Plated Steelcaps when the enemy has a threatening AD assassin or heavy auto-attack pressure. The 10% basic attack damage reduction on the boots is independent of your armor stat and reduces incoming auto damage from all sources. Guardian Angel as a second or third defensive item when you need a safety net against assassination.
- AP mid / mage: Zhonya's Hourglass when an AD assassin has a reliable kill window on you. The stasis active is often more valuable than the 50 armor: 2.5 seconds of untargetability either forces the assassin to waste their combo or lets your team collapse on them.
Do not build armor reactively against a full AP team. If no enemy champion has meaningful physical damage past basic attacks, every gold spent on armor delays a damage or sustain item. Check the enemy team composition before spending 2,400 to 3,300 gold on an armor purchase.
How to Counter Armor
Armor stacking reduces flat physical damage. The direct answer is armor penetration. The strategic answer is targeting enemies who have not built armor yet.
Lethality (Flat Armor Penetration)
Each point of lethality ignores one point of the target's effective armor. Lethality cannot reduce effective armor below zero. It is most efficient against low-armor targets: 30 lethality against a 30-armor mage is full penetration; the same 30 lethality against a 300-armor tank moves the damage multiplier from 25% to 27%. Full lethality guide with item table and crossover math.
Percent Armor Penetration
Lord Dominik's Regards (35% armor pen) treats the target's armor as multiplied by (1 minus the percent). At 100 armor, 35% pen reduces effective armor to 65. At 200 armor, it reduces effective armor to 130. Percent penetration scales with the target's armor and is mandatory when the enemy team has two or more dedicated armor stackers past 150 total armor.
In most AD games the efficient path is: lethality items early when the enemy team is squishy, then Lord Dominik's Regards as a third or fourth item once tanks begin buying dedicated armor. If the enemy team has no armor stackers, skip percent penetration and take a second damage item instead.
Armor Reduction
Flat armor reduction actually lowers the target's armor stat, unlike penetration which only affects the calculation. Black Cleaver stacks to 30% armor reduction over six hits, applied as a percentage, not flat. Nasus E reduces nearby enemy armor by a flat amount and can push armor below zero (at which point the target takes bonus physical damage instead of reduced). Armor reduction applies before penetration in the calculation order, making the two effects multiplicative.
Target Selection Over Resistance Stacking
The most efficient counter to a 300-armor tank is to stop targeting it. AD carries deal their highest damage-per-gold against targets at 30 to 60 armor: supports, mages, and other carries who have not itemized armor at all. If the enemy tank is stacking armor specifically to absorb your physical damage, force fights around objectives, let your AP teammates handle the frontline, and apply your physical damage to softer targets.
Physical damage is most effective when it is falling on unprepared enemies, not on tanks built around absorbing it.
