What is Armor and how does it reduce physical damage in TFT?

Armor is the physical-defense stat that mitigates incoming AD damage. The reduction formula is Armor / (100 + Armor), so 50 Armor cuts physical damage by ~33%, 100 Armor cuts it by 50%, and 200 Armor cuts it by ~67%. An equivalent way to read the same number: effective HP against physical damage equals max HP × (1 + Armor/100), i.e., 100 Armor doubles your physical EHP relative to HP alone. Armor does nothing against magic damage, and true damage ignores it entirely.

Does stacking Armor have diminishing returns?

Not in effective-HP terms. The percentage-reduction curve looks like it flattens — going from 0 to 100 Armor reduces damage by 50%, while going from 100 to 200 only adds another ~17 percentage points — but every point of Armor adds the same fixed slice of effective HP. Each +100 Armor adds another full max-HP bar of physical EHP, with no falloff. Where diminishing returns DO appear is against percent-Armor reduction (Sunder): a heavily Armor-stacked unit loses more raw Armor per Sunder hit, so a balanced HP + Armor profile is still better than going all-in.

Should I stack Armor or Health on a tank?

Both — they multiply. Effective HP against physical damage equals max HP × (1 + Armor/100), so adding HP is more valuable when you already have Armor (the HP gets multiplied), and adding Armor is more valuable when you already have a big HP pool (it multiplies a bigger base). Layered, they compound; isolated, either stat caps out at its own multiplier. The practical consequence: a tank with mid-range HP and mid-range Armor has more physical EHP than one with all the points poured into a single stat, and items that grant both at once are typically the most efficient.

Should I prioritize Armor or Magic Resist on my frontline?

Match the threat. Armor only mitigates AD damage; MR only mitigates AP damage. Each 100 Armor doubles your physical EHP (relative to HP alone), and each 100 MR doubles your magic EHP — so going all-in on one resist leaves the other damage type fully exposed. If the lobby's strongest carries are AD, prioritize Armor; if magic-heavy, prioritize MR; against mixed damage, balanced layering of both plus HP outperforms either solo stack. Items that grant both Armor and MR are usually the most flexible early scout choices when you don't yet know what you'll be fighting.

How does Sunder work, and does it stack from multiple sources?

Sunder is a percent-Armor reduction debuff applied to the target — most commonly via item effects (e.g., Last Whisper, which Sunders on both attacks and Abilities) or specific ability scripts. The percent-Sunder keyword does not stack. When multiple Sunder sources hit the same target, the duration refreshes but only one application is active at a time, mirroring Riot's standard "this effect does not stack" clause used on the Shred side. A separate, smaller class of effects applies flat Armor reduction (a small fixed value subtracted from the target's Armor) — those follow different stacking rules than the percent Sunder keyword, even when their tooltip text also reads "reduce Armor."

When flat and percent Armor reduction both apply, what's the order of operations?

Flat Armor reduction is applied first, then percent Sunder operates on the remaining Armor value, and finally the resistance formula runs against that final Armor. The practical consequence: stacking flat reduction first then percent Sunder gets diminishing efficiency from the Sunder — it operates on a smaller Armor value. Damage amplifiers (effects that read "deals X% more damage") are a separate stage applied post-mitigation, not during the Armor calculation. Resistances are floored at 0, so flat reduction past zero is wasted.

Can a unit's Armor go below zero, and does that amplify damage taken?

No — not in current TFT. Resistances are floored at 0. Once Sunder and other Armor-reduction effects bring a unit to 0 Armor, any further reduction is wasted: incoming physical damage is fully unmitigated (effectively true damage), but it isn't amplified. The reduction multiplier 100 / (100 + Armor) tops out at 1.0×. TFT diverged from base League around Set 9 (patch 13.16, August 2023), when Riot patched Samira so her Armor reduction could no longer push the stat below 0; the system has stayed floored at 0 across every set since.

Does Armor help against true damage or Burn ticks?

No. Armor only reduces incoming physical damage, so true damage of any kind passes through it untouched. Burn is the clearest example — its damage-over-time tick is dealt as true damage based on a percentage of the target's maximum Health, so neither Armor nor MR mitigates it. Armor also does nothing against magic damage. A unit with stacked Armor but a thin Health pool can still be melted by any source tagged true damage in its tooltip, since the only stat true damage interacts with is HP itself (and shields, which absorb true damage until consumed).

Armor

The physical-defense stat that reduces incoming AD damage. Tank items, the Bastion trait, and champions or items that grant flat Armor all feed into this mechanic, alongside the handful of effects that scale a bonus off a unit's Armor value. Sunder is its inverse — a debuff that reduces enemy Armor.

Listed in: Buffs

Items (65)

Refine list…

Adaptive Helm
- +20 MR
- +3 Mana Regen
Gain an additional 15% Mana from all sources. The holder gains an additional bonus based on their Role: Tanks and Fighters: Gain 30 Armor and Magic Resistance. Other Roles: Gain 10% Attack Damage and Ability Power.
Bramble Vest
- +50 Armor
Gain 6% max health. Take 5% reduced damage from attacks. When struck by any attack, deal @1StarAoEDamage@ magic damage to all adjacent enemies. Cooldown: 2 seconds
Crownguard
- +100 HP
- +20 Armor
- +20 AP
Combat Start: Gain a 25% max Health Shield for 8 seconds. When the Shield expires, gain 25% Ability Power.
Edge of Night
- +20 Armor
- +10% AD
- +15% AS
- +10 AP
At 60% Health, briefly become untargetable, shed negative effects, and heal 20% missing health.
Evenshroud
- +250 HP
- +20 MR
30% Sunder enemies within 2 hexes. Gain 15 Armor and Magic Resist for the first 15 seconds of combat. Sunder: Reduce Armor
Gargoyle Stoneplate
- +100 HP
- +25 Armor
- +25 MR
Gain 10 Armor and 10 Magic Resist for each enemy targeting the holder.
Last Whisper
- +15% AD
- +20% AS
- +20% Crit
Damage from attacks and Abilities 30% Sunder the target for 3 seconds. This effect does not stack. Sunder: Reduce Armor
Protector's Vow
- +25 Armor
- +25 MR
- +1 Mana Regen
Combat Start: Gain 20 Mana. At 40% Health, gain 15 Mana and a Shield equal to 20% max Health.
Steadfast Heart
- +250 HP
- +20 Armor
- +20% Crit
Gain 5% Durability. While above 50% Health, instead gain 15% Durability.
Sunfire Cape
- +150 HP
- +20 Armor
Gain 8% max Health. Every 2 seconds, deal 1% Burn and 33% Wound to an enemy within 2 hexes for 10 seconds. Burn: Deals a percent of the target's max Health as true damage every second Wound: Reduces healing received
Titan's Resolve
- +20 Armor
- +10% AS
Gain 2% Attack Damage and 2% Ability Power when attacking or taking damage, stacking up to 25 times. At full stacks, gain 10% Damage Amp and gain immunity to crowd control.
Chain Vest
- +20 Armor
Radiant Adaptive Helm
- +40 MR
- +7 Mana Regen
Gain an additional 30% Mana from all sources. The wearer gains an additional bonus based on their Role: Tank/Fighter: Gain 80 Armor and Magic Resistance. Marksman/Caster: Gain 40% Attack Damage and Ability Power.
Radiant Bramble Vest
- +100 Armor
Gain 12% max health. Take 10% reduced damage from attacks. When struck by any attack, deal @1StarAoEDamage@ magic damage to all adjacent enemies. Cooldown: 2 seconds
Radiant Crownguard
- +200 HP
- +40 Armor
- +40 AP
Combat Start: Gain a 50% max Health Shield for 8 seconds. When the Shield expires, gain 50% Ability Power.
Radiant Edge of Night
- +40 Armor
- +30% AD
- +30% AS
- +30 AP
At 60% Health, briefly become untargetable, shed negative effects, and heal all missing health.
Radiant Evenshroud
- +500 HP
- +40 MR
30% Sunder enemies within 3 hexes. Gain 50 Armor and Magic Resist for the first 20 seconds of combat. Sunder: Reduce Armor
Radiant Gargoyle Stoneplate
- +300 HP
- +50 Armor
- +50 MR
Gain 20 Armor and 20 Magic Resist for each enemy targeting the holder.
Radiant Last Whisper
- +45% AD
- +40% AS
- +40% Crit
Damage from attacks and Abilities 30% Sunder the target for the rest of combat. This effect does not stack. Sunder: Reduce Armor
Radiant Protector's Vow
- +50 Armor
- +50 MR
- +2 Mana Regen
Combat Start: Gain 40 Mana. At 40% Health, gain 30 Mana and a Shield equal to 50% max Health.
Radiant Steadfast Heart
- +600 HP
- +40 Armor
- +40% Crit
Gain 10% durability. While above 50% Health, instead gain 30% Durability.
Radiant Sunfire Cape
- +300 HP
- +40 Armor
Gain 16% max Health. Every 2 seconds, deal 2% Burn and 33% Wound to an enemy within 2 hexes for 10 seconds. Burn: Deals a percent of the target's max Health as true damage every second Wound: reduces healing received
Radiant Titan's Resolve
- +40 Armor
- +20% AS
Gain 4% Attack Damage and 4% Ability Power when attacking or taking damage, stacking up to 25 times. At full stacks, gain 20% Damage Amp and gain immunity to crowd control.
Aegis of Dawn
- +400 HP
- +50 Armor
Every 2.5 seconds, steal 3 Armor from enemies within 1-hex and heal 15%–50% (by Stage) of the holder's Armor. If Aegis of Dusk is also equipped, trigger this item's effect every 1.25 seconds instead. Healing increases based on Stage.
Death's Defiance
- +40 Armor
- +25% AD
- +15% AS
- +25% Omnivamp
50% of the damage the holder receives is instead dealt over 4 seconds as non-lethal damage. [Unique - only 1 per champion]
Eternal Winter
- +200 HP
- +20 Armor
Enemies who damage the holder are 20% Chilled for 1.5 seconds. After 7 Chills from this item, the attacker is Stunned instead (Cooldown: 15 seconds). [Unique - only 1 per champion] Chill: reduce Attack Speed Stun: cannot move, attack, or cast Abilities
Forbidden Idol
- +200 HP
- +25 Armor
- +25 MR
Shields have 50% of their value converted to max Health instead.
Hullcrusher
- +60 Armor
- +60 MR
Combat Start: If there are no adjacent allies, gain 400 Health, 10% Attack Damage, and 10% Ability Power.
Infinity Force
- +300 HP
- +30 Armor
- +30 MR
- +30% AD
- +30% AS
- +30 AP
Tons of EVERYTHING!
Lesser Mirrored Persona
- +100 HP
- +10 Armor
- +10 MR
- +10% AD
- +10% AS
- +10 AP
Share 15% of the holder's bonus Attack Damage, Ability Power, Attack Speed, Armor, Magic Resist, and Health with other Mirrored Persona holders. Can't be Reforged Unique: one per champion
Lightshield Crest
- +55 Armor
- +55 MR
Every 3 seconds, Shields the lowest percent Health ally for 70% of the holder's combined Armor and Magic Resist for 5 seconds. On death grants this shield to all allies.
Locket of the Iron Solari
- +150 HP
Combat start: The holder and allies within 2 hexes in the same row gain a 250 Shield, 20 Armor, and 20 Magic Resist for 20 seconds. [Support item]
Mirrored Persona
- +100 HP
- +10 Armor
- +10 MR
- +10% AD
- +10% AS
- +10 AP
Every 6 player combats gain a lesser copy of Mirrored Persona ( /6). Share 15% of the holder's bonus Attack Damage, Ability Power, Attack Speed, Armor, Magic Resist, and Health with other Mirrored Persona holders. Can't be Reforged, Lesser copies do not produce copies. Unique: one per champion
Mogul's Mail
- +300 HP
Grants 1 Armor, 1 Magic Resist, and 5 Health when taking damage, stacking up to 35 times. At full stacks, grant 1 gold and continue gaining 1 gold every 11 seconds. [Unique - only 1 per champion]
Seeker's Armguard
- +10 Armor
- +10 MR
- +25 AP
- +20% Omnivamp
Takedowns increase the holder's Armor, Magic Resist, and Ability Power by 20.
Shadow Puppet
- +10 Armor
- +10 MR
- +10% AS
Spawn a clone that copies the holder's items. The clone has 60% max Health and deals 40% damage. [Unique - only 1 per champion]
Silvermere Dawn
- +80 Armor
- +80 MR
- +140% AD
Grants immunity to Stuns and the holder's attacks Stun the target for 0.8 seconds. The holder's Attack Speed is locked at 0.5.
The Indomitable
- +500 HP
- +20 Armor
- +20 MR
The holder's Move Speed is drastically reduced. Gain 15% max Health, stun immunity, and pull the current target into melee range.
Thresh's Lantern
- +400 HP
- +35 Armor
- +35 MR
After 6 seconds of combat, pull the leftmost benched unit onto the battlefield. While that unit lives, 20% of all damage the holder would take is redirected to them. Traits of champions flung onto the board do not become active
Trickster's Glass
- +10 Armor
- +10 MR
- +10% AS
- +15% Crit
Summon a clone with 70% base Health and +10% max Mana. You cannot equip items to the clone. The clone benefits from active traits [Unique - only 1 per champion]
Unending Despair
- +350 HP
- +40 Armor
Whenever a Shield on the holder breaks, 150% of that Shield's initial value is dealt to the nearest enemy as magic damage.
Wit's End
- +400 HP
- +20 Armor
- +20 MR
- +25% AS
Attacks deal 30–100 (by Stage) bonus magic damage. Heals the holder for 30% of all magic damage dealt. Damage increases based on Stage.
Zhonya's Paradox
- +25 Armor
- +25 MR
- +25 AP
Once per combat at 40% Health, become invulnerable and untargetable for 3 seconds. [Unique - only 1 per champion]
Arbiter Emblem
- +20 Armor
- +20 MR
- +30% AS
The holder gains the Arbiter trait.
```
Scribe a unique divine law, allowing you to choose an effect to apply to Arbiters when a chosen cause occurs.
```
2
Choose a cause and effect for your law
3
Effects are stronger.
Bastion Emblem
- +30 Armor
- +30 MR
The holder gains the Bastion trait. After the first 10 seconds of combat, the holder gains 70% Attack Speed.
```
Your team gains 15 Armor and Magic Resist.

Bastions gain more, and the value doubles in the first 10 seconds of combat.
```
2
16
4
40
6
60
Meeple Emblem
- +20 Armor
- +20 MR
- +2 Mana Regen
The holder gains the Meeple trait and 4% Damage Amp and 50 Health per.
```
Meeple attract Meeps that empower Meeple abilities in meepy ways. They also gain bonus Health.

Cloning time = Champion cost
```
3
2, 100
5
3, 350
7
4, 450
10
6, 550
N.O.V.A. Emblem
- +200 HP
- +20% Crit
The holder gains the N.O.V.A. trait. N.O.V.A. Strike: Gain 25% Attack Speed and 10 Armor and Magic Resist. Other allies gain 10% Attack Speed and 10 Armor and Magic Resist.
```
Aatrox: Ally Damage 30% Shred and Sunders enemies
Caitlyn: Grant allies 20% Attack Speed
Akali: Allies gain Precision
Maokai: Allies heal 12% max Health
Kindred: Shield the strongest Tank for 800
Emblem: Allies deal 10% stacking bonus true damage
```
2
6 seconds into combat, N.O.V.A. grant a power surge to allies based on champions.
5
Gain a Striker selector. The chosen N.O.V.A. activates their Strike during the power surge.
Vanguard Emblem
- +20 Armor
- +20 MR
The holder gains the Vanguard trait. Gain 2% Ability Power whenever an ally gains a shield.
```
Vanguards gain 5% Durability while Shielded. 

Combat start and 50% Health: Gain a max Health Shield for 10 seconds.
```
2
16% max Health
4
30% max Health
6
40% max Health
Voyager Emblem
- +20% AD
- +20 AP
The holder gains the Voyager trait. Combat Start: The holder and allies within 1 hex in the same row gain a bonus based on the holder's role. - Tanks: 10 Armor and Magic Resist - Fighters/Assassins: 10% Omnivamp - Other Roles: 10% Attack Speed
```
Combat Start: Your Tanks gain a Shield for 15 seconds. Your other allies gain Damage Amp. 

Voyagers gain double.
```
2
175 Shield; 9%
3
250 Shield; 15%
4
350 Shield; 18%
5
500 Shield; 22%
6
700 Shield; 27%
Cyclonic Slicers
- +15 Armor
- +15 MR
- +20% AD
- +20 AP
Gain 3 orbiting razors. Razors deal ? magic damage, and 30% Shred and Sunder enemies for 4 seconds. Deal 10% increased damage to Shredded or Sundered enemies. Damage increases based on Stage. Recommended Roles: Attack or Magic Fighter
Deep Freeze
- +550 HP
- +30 Armor
- +30 MR
The first time you fall below 90%, 60%, 40%, and 20% health, gain a 20% max health shield for 4 seconds. When this happens, release a frost nova that stuns enemies within 2 hexes for 2 seconds and deals magic damage equal to 15% of their max Health. The radius increases by 1 each nova. Recommended Roles: Attack or Magic Tank
Iceblast Armor
- +250 HP
- +30 Armor
- +30 MR
The first time you fall below 70% and 35% health, gain a 25% max health shield for 4 seconds and release a frost nova that stuns enemies within 3 hexes for 2 seconds. Recommended Roles: Attack or Magic Tank
Leonine Lamentation
- +400 HP
- +40 Armor
- +40 MR
Every 15% max health lost, fire crescent projectiles in 3 lines dealing physical damage equal to 50% of the holder's Armor and Magic Resist. Steal 10 Armor and Magic Resist from all enemies hit. Recommended Roles: Attack or Magic Tank
Lioness's Lament
- +200 HP
- +30 Armor
- +30 MR
Every 15% max health lost, fire crescent projectiles in a line dealing physical damage equal to 50% of the holder's Armor and Magic Resist. Steal 4 Armor and Magic Resist from all enemies hit. Recommended Roles: Attack or Magic Tank
Omniweapon
- +10000 HP
- +100 Armor
- +100 MR
- +100% AD
- +100% AS
- +100 AP
- +75% Crit
- +100% Omnivamp
- +10 Mana Regen
The pinnacle of Anima technology.
Unceasing Cyclone
- +40 Armor
- +40 MR
- +30% AD
- +30 AP
Gain 6 orbiting razors. Razors deal ? true damage, and 30% Shred and Sunder enemies for the rest of combat. Deal 30% increased damage to Shredded or Sundered enemies. Damage increases based on Stage. Recommended Roles: Attack or Magic Fighter
Malware Matrix
- +15% AS
- +10% Omnivamp
Attack Champion: Dealing physical damage to an enemy reduces the target's Armor by 2. Magic Champion: Dealing magic damage to an enemy reduces the target's Magic Resist by 2. Recommended users: Master Yi and Pyke. Ability Damage Cooldown: 0.75 seconds.
Malware Matrix
- +15% AS
- +10% Omnivamp
Attack Champion: Dealing physical damage to an enemy reduces the target's Armor by 2. Magic Champion: Dealing magic damage to an enemy reduces the target's Magic Resist by 2. At (4): If the holder is Psionic, every 3rd attack cleaves, dealing 75 physical damage to nearby enemies. Recommended users: Master Yi and Pyke. Ability Damage Cooldown: 0.75 seconds.
AP Rounds

Attacks and Abilities ignore 30% of enemy Armor
AP Rounds+

Attacks and Abilities ignore 60% of enemy Armor
Heavy Plating

Gain 300 Base Health, 20 Armor, and 20 Magic Resistance.
Meltthrough

Every second, reduce the Armor of enemies within 2-hexes by 4, doubled for adjacent enemies.
Reactive Armor

Taking damage from enemies grants 4 bonus Armor and Magic Resistances, up to 50.
Ripper Bullets

Attacks reduce enemy Armor and Magic Resistance by 1.
Ripper Bullets+

Attacks reduce enemy Armor and Magic Resistance by 2.

Augments (11)

Refine list…

Bronze For Life II Prismatic

Your team gains 2% Damage Amp and 4 Armor and Magic Resist for each Bronze-tier trait.

Bodyguard Training Gold

Allies gain 15 Armor and Magic Resist, increased by 2 per player level.

Gizmos & Gadgets Championship, 2022

Climb The Ladder II Gold

Each time an ally dies, allies that share at least one trait with them gain 7% Ability Power, 7% Attack Damage, 6 Armor, and 6 Magic Resist.

Group Hug II Gold

Combat start: Allies grant other adjacent allies 9 Armor and Magic Resist. This effect stacks.

Plot Armor Gold

Your team gains 8 Armor and Magic Resist. After falling below 50% Health, increase this to 40 for the rest of combat.

Climb The Ladder I Silver

Each time an ally dies, allies that share at least one trait with them gain 3.5% Ability Power, 3.5% Attack Damage, 3.5 Armor, and 3.5 Magic Resist.

Corrosion Silver

Enemies in the first two rows lose 4 Armor and Magic Resist every 2 seconds.

Group Hug I Silver

Combat start: Allies grant other adjacent allies 6 Armor and Magic Resist. This effect stacks.

Lineup Silver

Your team gains 2 Armor and Magic Resist for each ally that starts combat in the front two rows.

Size Matters Silver

Gain a Giant's Belt. After a champion starts combat with more than 3600 max Health, gain a Warmog's Armor.

Twin Guardians Silver

If you have exactly 2 allies in your first row, grant them 100 bonus Health, 35 Armor, and 35 Magic Resist.

Champions (7)

1 Aatrox

Attack Tank

Stellar Slash
Heal 325 / 400 / 650 , then deal 80 / 120 / 180  physical damage to the current target.

N.O.V.A. Strike: Cleave the battlefield, briefly knocking up all enemies and dealing   physical damage.

1 Leona

Magic Tank

Shield of Daybreak
Gain   Shield for 4 seconds. Bash the current target, dealing 100 / 150 / 225  magic damage and stunning them for 1.75 / 1.75 / 2 seconds.

1 Poppy

Magic Tank

Huddle Up!
Gain 400 / 475 / 575  Shield for 4 seconds. For the duration, allies within two hexes gain 15 / 25 / 60  Armor and Magic Resistance.

Meep Bonus: Meeps grant 125 / 160 / 210  Shield to the nearest ? allies for 4 seconds.

2 Akali

Attack Fighter

Star Strike
Reposition next to the target to strike the most enemies. Then throw 5 piercing kunai, each dealing 43 / 65 / 97  physical damage to the first enemy hit, reduced to   for each subsequent target. Kunai remove 1 Armor, 2 if they crit.

N.O.V.A. Strike: Slice all enemies, applying Wound and a bleed that deals   physical damage each second. Kunai increase the damage of the bleed by 12%.

2 Jax

Magic Tank

Counter Star-ike
Enter a defensive stance for 3 seconds, reducing incoming damage by 20 / 25 / 30 and gaining 400 / 450 / 500  Shield. When the stance ends, strike all nearby enemies, dealing   magic damage and Stunning them for 1 / 1.25 / 1.5 second(s).

4 Rammus

Magic Tank

Gravitational Spin
Gain 675 / 825 / 2000  shield for 4 seconds. Then, strike enemies in a three hex line, dealing 50.5 / 75.75 / 711  magic damage.

Meep Bonus: Reduce the damage of incoming attacks by ? . After being attacked 20 times, deal   magic damage in a two hex radius.

4 The Mighty Mech

Attack Tank

Gravity Matrix
Enter a defensive stance for 4 seconds gaining 20 / 20 / 60% Durability. While in the defensive stance, attract nearby enemy projectiles and heal 900 / 1300 / 3000  over the duration. When this ends, release a shockwave that deals   as physical damage in a 2-hex range.

Traits (4)

Refine list…

Bastion

Your team gains 15 Armor and Magic Resist.

Bastions gain more, and the value doubles in the first 10 seconds of combat.

Eradicator

Enemies have 10% less Armor and Magic Resist.

Redeemer

Stargazer

Stargazers chart a different constellation every game. This game: The Mountain

Every 5 player combats, gain a Stargazer Emblem. Stargazers in empowered hexes gain various bonuses.

More hexes reveal at each player level

Frequently asked questions

What is Armor and how does it reduce physical damage in TFT?
Armor is the physical-defense stat that mitigates incoming AD damage. The reduction formula is Armor / (100 + Armor), so 50 Armor cuts physical damage by ~33%, 100 Armor cuts it by 50%, and 200 Armor cuts it by ~67%. An equivalent way to read the same number: effective HP against physical damage equals max HP × (1 + Armor/100), i.e., 100 Armor doubles your physical EHP relative to HP alone. Armor does nothing against magic damage, and true damage ignores it entirely.
Sources
Does stacking Armor have diminishing returns?
Not in effective-HP terms. The percentage-reduction curve looks like it flattens — going from 0 to 100 Armor reduces damage by 50%, while going from 100 to 200 only adds another ~17 percentage points — but every point of Armor adds the same fixed slice of effective HP. Each +100 Armor adds another full max-HP bar of physical EHP, with no falloff. Where diminishing returns DO appear is against percent-Armor reduction (Sunder): a heavily Armor-stacked unit loses more raw Armor per Sunder hit, so a balanced HP + Armor profile is still better than going all-in.
Sources
Should I stack Armor or Health on a tank?
Both — they multiply. Effective HP against physical damage equals max HP × (1 + Armor/100), so adding HP is more valuable when you already have Armor (the HP gets multiplied), and adding Armor is more valuable when you already have a big HP pool (it multiplies a bigger base). Layered, they compound; isolated, either stat caps out at its own multiplier. The practical consequence: a tank with mid-range HP and mid-range Armor has more physical EHP than one with all the points poured into a single stat, and items that grant both at once are typically the most efficient.
Sources
Should I prioritize Armor or Magic Resist on my frontline?
Match the threat. Armor only mitigates AD damage; MR only mitigates AP damage. Each 100 Armor doubles your physical EHP (relative to HP alone), and each 100 MR doubles your magic EHP — so going all-in on one resist leaves the other damage type fully exposed. If the lobby's strongest carries are AD, prioritize Armor; if magic-heavy, prioritize MR; against mixed damage, balanced layering of both plus HP outperforms either solo stack. Items that grant both Armor and MR are usually the most flexible early scout choices when you don't yet know what you'll be fighting.
Sources
- How Armor and Magic Resistance works in TFT — LeDuck (Tacter) (opens in new tab)
- Resistances (TFT) — League of Legends Wiki (opens in new tab)
How does Sunder work, and does it stack from multiple sources?
Sunder is a percent-Armor reduction debuff applied to the target — most commonly via item effects (e.g., Last Whisper, which Sunders on both attacks and Abilities) or specific ability scripts. The percent-Sunder keyword does not stack. When multiple Sunder sources hit the same target, the duration refreshes but only one application is active at a time, mirroring Riot's standard "this effect does not stack" clause used on the Shred side. A separate, smaller class of effects applies flat Armor reduction (a small fixed value subtracted from the target's Armor) — those follow different stacking rules than the percent Sunder keyword, even when their tooltip text also reads "reduce Armor."
Sources
When flat and percent Armor reduction both apply, what's the order of operations?
Flat Armor reduction is applied first, then percent Sunder operates on the remaining Armor value, and finally the resistance formula runs against that final Armor. The practical consequence: stacking flat reduction first then percent Sunder gets diminishing efficiency from the Sunder — it operates on a smaller Armor value. Damage amplifiers (effects that read "deals X% more damage") are a separate stage applied post-mitigation, not during the Armor calculation. Resistances are floored at 0, so flat reduction past zero is wasted.
Sources
Can a unit's Armor go below zero, and does that amplify damage taken?
No — not in current TFT. Resistances are floored at 0. Once Sunder and other Armor-reduction effects bring a unit to 0 Armor, any further reduction is wasted: incoming physical damage is fully unmitigated (effectively true damage), but it isn't amplified. The reduction multiplier 100 / (100 + Armor) tops out at 1.0×. TFT diverged from base League around Set 9 (patch 13.16, August 2023), when Riot patched Samira so her Armor reduction could no longer push the stat below 0; the system has stayed floored at 0 across every set since.
Sources
Does Armor help against true damage or Burn ticks?
No. Armor only reduces incoming physical damage, so true damage of any kind passes through it untouched. Burn is the clearest example — its damage-over-time tick is dealt as true damage based on a percentage of the target's maximum Health, so neither Armor nor MR mitigates it. Armor also does nothing against magic damage. A unit with stacked Armor but a thin Health pool can still be melted by any source tagged true damage in its tooltip, since the only stat true damage interacts with is HP itself (and shields, which absorb true damage until consumed).
Sources

Description

Items (65) #

Augments (11) #

Champions (7) #

Traits (4) #

Frequently asked questions

Items (65)

Augments (11)

Champions (7)

Traits (4)