LoL Armor, Magic Resist and Penetration Explained (2026)

Every point of damage in League of Legends passes through the same short list of rules before it reaches a health bar: what type it is, how much armor or magic resist the target has, and how much of that resistance the attacker ignores. Learn the rules once and a lot of item decisions stop being guesswork — when lethality beats percent penetration, why tanks don't fall off when they keep buying armor, and when to build health instead of resists. This guide covers all of it for patch 26.22, with the formulas from the official League of Legends wiki and worked examples you can check.

The three damage types

Each ability tooltip says which type it deals, and the colour of damage numbers in game matches the type. A champion's split matters for everyone else's shopping: an enemy team that deals almost all physical damage makes armor twice as valuable as magic resist.

The resist formula

The blocked percentage climbs more slowly the more you have — 100 armor blocks 50%, but doubling it to 200 only adds about 17 points. That looks like diminishing returns, and it's the most common misunderstanding about resists.

Effective health: why resists don't fall off

Look at it from the attacker's side instead. The wiki's effective health formula is health × (1 + resist ÷ 100): "every 1 point of armor adds 1% to the effective health pool". 1,000 health with 100 armor takes 2,000 physical damage to kill; with 200 armor it takes 3,000. Each point added the same amount, so a tank's twentieth armor point is worth as much as the first — against that damage type.

That also tells you when to buy health instead. With the gold values from our gold efficiency guide (1 armor = 20 gold, 1 health ≈ 2.67 gold), 300 gold buys either 15 armor or about 112 health. Working through the formula, armor gives more effective health whenever your health is above 750 × (1 + armor ÷ 100) — about 1,500 health if you already have 100 armor. Below that, health first; above it, resists. That's BoostPirate's arithmetic on the wiki's formula, and a good rule of thumb rather than a law: item passives, healing and true damage all shift it.

How much armor and magic resist champions start with

Every champion grows resists with each level. The wiki's champion tables give the ranges:

Two things follow. Squishy champions start with little armor, so a small amount of flat penetration removes a big share of it — the lethality section below shows how much. And ranged champions' low magic resist is why burst mages are at their best against back lines.

The order of reduction and penetration

When an attacker carries several ways of cutting resists, the game applies them in a fixed order. From the official wiki:

1. Flat reduction — subtracts a fixed amount from the target's resist, bonus resist first. The only step that can go below zero.
2. Percentage reduction — multiplies the resist, as Black Cleaver's Carve does (6% armor a stack, up to 5 stacks (30%)).
3. Percentage penetration — Lord Dominik's Regards and Serylda's Grudge (35%), Void Staff (40%) — treats the resist as lower for your damage only.
4. Flat penetration (lethality) — subtracts a flat amount, but never below zero.

Reduction changes the target's actual resist, so it helps every teammate hitting that target; penetration only helps the champion who has it. The wiki's worked example: a target with 300 armor, hit by 30 flat reduction, 30% reduction, 45% bonus-armor penetration and 10 lethality ends up with 122.3 effective armor.

Lethality or percent penetration?

Lethality has been a flat 1:1 value since patch 14.1, when Riot removed its level scaling. That makes the comparison easy: flat penetration removes the same number of points from everyone, percentage penetration removes more from targets with more armor. Here is 18 lethality (Hubris, Axiom Arc, Profane Hydra or Umbral Glaive) against 35% penetration (Lord Dominik's Regards) — the target's armor after each, and the damage share that gets through:

The break-even point is where 18 equals 35% of the armor: about 51 armor. Below it lethality removes more; above it percentage penetration does. Squishy carries sit near the bottom of the table for most of the game, which is why assassins build lethality first and fighters or marksmen facing tanks finish with Lord Dominik's Regards or Serylda's Grudge. Lethality items on the wiki's table: Bastionbreaker 22, Axiom Arc 18, Hubris 18, Profane Hydra 18, Umbral Glaive 18, Edge of Night 15, Serpent's Fang 15, Spectral Cutlass 15, The Collector 10, Voltaic Cyclosword 10, Serrated Dirk 10, The Brutalizer 5.

Magic penetration

Magic resist follows exactly the same order — flat reduction, percentage reduction, percentage penetration, flat penetration — and the same rule that penetration stops at zero. The wiki adds that penetration applies to all magic damage, including damage to turrets. The sources on the wiki's tables:

The same lethality logic applies to mages. Sorcerer's Shoes' flat 12 matter most early, when targets have 30–40 magic resist; Void Staff or Cryptbloom come later, when the enemy has built some. Mid laners who finish their Role Quest upgrade Sorcerer's Shoes into Spellslinger's Shoes for free — 18 flat and 7% on one pair of boots.

True damage

True damage skips the whole pipeline. The official wiki: unless stated otherwise it ignores armor, magic resist and damage-reduction effects such as Exhaust — but shields absorb it like any other damage. Sources you'll meet on the Rift:

IgniteTrue damage over time and Grievous Wounds; it can't be amplified.

summoner

Smite600 / 1,000 / 1,400 (Smite, Unleashed, Primal) true damage to monsters.

summoner

Ahri's Orb of DeceptionMagic damage on the way out, true damage on the way back (Riot's ability text).

ability

Elder DragonAspect of the Dragon burns for 75–225 true damage over 2.25 seconds and executes below 20% health.

buff

Elixir of Sorcery25 bonus true damage to champions and turrets while it lasts.

elixir

You can't build resists against true damage, but you can still play against it: health makes flat true damage such as Ignite a smaller share of your bar, shields soak it, and against a percent-health or true-damage champion, health and healing items keep more value than a third armor item. The summoner spells guide covers Ignite and Exhaust.

Building resists: armor or magic resist?

1. Read the enemy's damage, not their names. Open the scoreboard after ten minutes: who has kills and items? A fed AD carry and an AD assassin make armor your first defensive buy.
2. Answer the biggest threat first. One defensive item against the champion killing you does more than splitting gold across both resists.
3. Mind the health balance. With little health, buy health or a mixed item first; once you're above the break-even point above, resists give more.
4. Use boots and runes. Plated Steelcaps or Mercury's Treads are cheap resist; the Resolve rune Unflinching adds +10 armor and magic resist while you're crowd-controlled by a champion, and for 2 seconds after.
5. Remember turrets. Turrets and dragons have 30% armor penetration — diving into one hurts more than its numbers suggest.

Most armor on one item

Thornmail, Randuin's Omen and Frozen Heart give 75 armor; Dead Man's Plate 55 — the official wiki's item table.

Most magic resist on one item

Kaenic Rookern gives 80 magic resist, Force of Nature 55 and Spirit Visage 50; Negatron Cloak, Abyssal Mask, Jak'Sho and Wit's End give 45.

Common damage and resist mistakes

Read next: gold efficiency, the crowd control guide, teamfighting and the items guide.