TFT Durability, Damage Amp and True Damage: What They Mean for Your Items

TL;DR: Durability pays most on your biggest health bar: 15% durability beats 500 more Health once a unit has about 2,833 Health. Damage Amp keeps its value as your AD or AP grows, which is why Riot’s 18.4 notes call it too valuable. So once a carry has some AD, the first amp source beats more AD point for point. Sunder and Shred beat a 20% amp only above 125 of the resist. Burn scales with the target’s Health, so it does most against the biggest tank. Riot has published little on how these stack, so these sums rest on working rules, and they say so.

Worked examples are hypotheticals: sums, not records of real games. The formulas here are working rules, not Riot’s. Where a Riot page says something, it’s linked, and where none was found, the page says so. senseos.gg’s combat keywords page defines the terms, the tank guide and damage guide cover the wider formulas, and this page turns the three stats into item choices.

What has Riot actually published?

Not much. Here’s what was found, and what wasn’t:

Question	What Riot says	Where
What is Durability?	A short gloss: damage reduction	14.16, August 2024
How does Damage Amp combine with other stats?	It multiplies with AD, AP and crit, which Riot says makes it too valuable	18.4, October 2026
What is true damage?	Burn is a share of max Health dealt as true damage each second	Enchanted Wilds overview, July 2026
Can true damage be countered?	Riot says it has limited counterplay	14.18, September 2024
Do tank stats multiply?	Riot speaks of tank items having multiplicative value	17.1, April 2026
How does Durability from two sources combine?	No Riot page found
How does Damage Amp from two sources combine?	No Riot page found. 17.1 and 14.23 say some sources stack, without the sum
What is the Armor or Magic Resist formula?	No Riot page found
Does Durability reduce true damage?	No Riot page found
Does Damage Amp raise true damage?	No Riot page found

Every sum below is arithmetic on a working rule. If your tooltip disagrees, your tooltip wins.

What is durability worth?

On the working rule that durability cuts damage taken by its percentage, your unit survives 1 / (1 - durability) times as long:

Durability	Effective Health	Set 18 example at patch 18.6
5%	1.05 times	Attuned, on Alune’s low moon (18.5)
10%	1.11 times	Spirit Visage (18.4, 8% in the game data files)
15%	1.18 times	Golden Dragon on a Mogul’s Mail holder (18.2)
18%	1.22 times	Radiant Spirit Visage (18.4, 15% in the game data files)
30%	1.43 times	Juggernaut (4), on a Juggernaut (18.4)
42%	1.72 times	Juggernaut (6), on a Juggernaut (18.4)

Durability against Health. Durability is a percentage, so it pays more on a bigger health bar. Health is a flat amount, so it pays less. Take a hypothetical choice of 500 Health or some durability:

Unit’s Health now	+500 Health	+10% durability	+15% durability
1,000	+50%	+11%	+18%
2,000	+25%	+11%	+18%
3,000	+17%	+11%	+18%
4,000	+13%	+11%	+18%

The lines cross at about 2,833 Health for 15% durability and 4,500 for 10%. Below that, take Health first. Above it, take durability. The same sum says durability belongs on your main tank, not on a thin unit in front of it.

Durability against resists. Say a hypothetical tank has 2,000 Health, 60 Armor and 60 Magic Resist, and takes half physical and half magic damage. On the tank guide’s working rule that every 100 of a resist doubles your Health against that damage, here’s what each choice adds:

Add	Effective Health against that mix	Change
Nothing	3,200
40 Armor	3,556	+11%
10% durability	3,556	+11%
15% durability	3,765	+18%
500 Health	4,000	+25%
40 Armor and 40 Magic Resist	4,000	+25%

So one resist alone is worth about 10% durability against a mixed lobby. It’s worth more if the lobby leans that way: all physical, and 40 Armor is +25%. Scout first. Durability doesn’t need that, and Sunder and Shred take a share of resists but, on these sums, leave durability alone.

Steadfast Heart has a switch. By the game data files, it’s 15% above half Health and 5% below. So half your Health gets 15% and half gets 5%, and you last 0.5/0.85 + 0.5/0.95, or about 1.11 times as long. That’s the same as a flat 10.3% or so. Riot’s 18.4 notes call Spirit Visage its weakest tank item and Crownguard the best wherever a unit can build it, and that’s about whole items. These sums price one stat at a time, so use them to choose between stats, not to rank items.

Does durability stack?

No Riot page was found that says. There are two readings, and the gap depends on how high you go:

Two sources	Added	Multiplied	Effective Health, added	Effective Health, multiplied
10% and 10%	20%	19%	1.25 times	1.23 times
20% and 15%	35%	32%	1.54 times	1.47 times
42% and 15%	57%	About 51%	2.33 times	2.03 times

The tank guide uses the multiplied reading as a working rule. At low durability the choice barely matters. On a Juggernaut (6) it does: adding a 15% item is 35% more effective Health on one reading and 18% on the other. So before you pile durability on a unit that already has a lot, read the number on its tooltip.

What is Damage Amp worth?

It multiplies, and that’s its whole advantage. Riot’s 18.4 notes cut Ivern’s Mushroom hexes for that reason, calling amp too valuable because it multiplies with AD, AP and crit. AD and AP don’t work that way. They add to what the unit already has, so each new point counts for less:

The unit’s bonus AD now	+20% AD	+55% AD (a Deathblade, by the game data files)	First 20% Damage Amp
None	+20%	+55%	+20%
+50%	+13%	+37%	+20%
+100%	+10%	+28%	+20%
+150%	+8%	+22%	+20%

So a Deathblade is still the larger jump if the numbers look like this, but it shrinks while the amp doesn’t. That column counts only its AD: Riot’s 13.3 notes (January 2025) and the game data files also give it 10% Damage Amp, so the whole item does more. Compare sources on the same footing. Going by the game data files, Striker’s Flail lists a flat 10% Damage Amp and adds 5% a stack on crits, up to 4 stacks, and Titan’s Resolve gives 10% at full stacks. The stacks need time to build, so count how long your fights last.

A second amp source is worth a little less, or the same. Riot’s 14.23 and 17.1 notes say some sources stack, without saying how. If they add, two 20% sources are 1.4 times, and the second is about 17% more. If they multiply, they’re 1.44 times, and the second is 20% more.

The damage guide has the wider rule: fill the bucket you don’t have. Amp is one of those buckets, and this table shows why it’s usually an empty one worth filling.

Amp and durability meet. On these working rules they multiply against each other, so 100 damage with 20% amp into 15% durability is 100 x 1.2 x 0.85, or 102. Into 20% durability it’s 96. So a carry with 20% amp roughly cancels the tank’s 15%, and doesn’t cancel 20%.

Which beats a tank: Sunder, amp or Burn?

It depends on the target’s Armor and Health. The game data files give Last Whisper and Evenshroud a 30% Sunder on Armor, and Void Staff and Ionic Spark a 30% Shred on Magic Resist. On the working rule that 100 of a resist halves damage, 100 physical damage goes through like this:

Target’s Armor	Damage taken	With 30% Sunder	More damage
50	67	74	+11%
100	50	59	+18%
200	33	42	+25%
300	25	32	+29%

Against a flat 20% amp, Sunder pulls ahead above 125 Armor. Against a 15% amp, it’s above about 77. Now add Burn. By the game data files, Morellonomicon, Red Buff and Sunfire Cape deal 1% Burn each second. Here’s a hypothetical carry dealing 400 physical damage a second before Armor, with each option on its own:

Target	Damage a second	Sunder adds	20% amp adds	1% Burn adds
Big tank: 5,000 Health, 200 Armor	133	33	27	50
Frontliner: 3,000 Health, 100 Armor	200	35	40	30
Backliner: 1,500 Health, 50 Armor	267	30	53	15

Read it by what you keep losing to:

• You can’t break the big tank. Burn adds most here, and Sunder comes next. Burn items also carry Wound, which the itemization guide covers, and that may matter more than the Burn.
• You lose to normal boards. The amp does best against the rest of the lobby, so a damage item with amp is the steady pick.
• Several units deal your physical damage. Sunder helps all of them, where the amp on one item helps only its holder. That sum favors Evenshroud or Last Whisper on a board with more than one physical damage dealer.

What about true damage?

Riot’s pages use the term without spelling out what it skips. The Enchanted Wilds overview calls Burn true damage, and Riot’s 14.18 notes say true damage has limited counterplay. No Riot page was found that says Armor and Magic Resist don’t apply, but that’s the working reading. So against 200 Armor, 100 physical damage is about 33, and 100 true damage stays 100.

These are Set 18 examples at patch 18.6:

Source	Number	What it means for items
Burn items	1% of max Health a second, by the game data files. That’s 10 a second on a 1,000-Health unit, 30 on 3,000 and 60 on 6,000	Scales with the target, so it adds most against big tanks
Inferno	1/1/3/4% Burn (18.3), and its Burns stack with other Burns, per Riot’s Part I page	At the top level that’s 120 a second on 3,000 Health, so a Burn item adds on top of it
Executioner (3) and (4)	Bleed of 25% and 35% (18.4), as bonus true damage over 3 seconds by the game data files	Damage that resists don’t cut, on the working reading, so Sunder or Shred helps that part less

So don’t build around Burn’s damage alone. In the table above it adds least on a backliner and most on a tank. No Riot page was found on whether Durability or Damage Amp changes true damage.

Don’t mix up the names. Riot’s November 2 dev post names a True Damage trait for Set 19. That’s a band and a trait, not this damage type. The Set 19 page covers what Riot has shown.

What should you do with your items?

Your spot	The call	Why
Tank under about 2,800 Health	Health first	+500 Health beats 15% durability there
Tank over about 4,500 Health	Durability first	10% durability beats +500 Health from there
Lobby leans one damage type	That resist	40 points is +25% on a 60-Armor unit, on the working rule
Mixed lobby	A stat that covers both	One resist alone is about 10% durability
Unit already has a lot of durability	Read the tooltip first	The second source is unpublished, and the readings split widely
Carry with no bonus AD	AD or AP first	It’s the larger jump until bonus stats build up
Carry with +100% AD or more	Amp over more AD, if you’re choosing	20% amp stays +20%, and 20% AD falls to +10%
Target over 125 Armor	Sunder over a 20% amp	+29% at 300 Armor
Can’t break one huge tank	Burn, then Sunder	Burn scales with its Health
Several physical damage dealers	Sunder	It helps them all

Real items bundle several stats, and Riot’s whole-item view in 18.4 still stands, so use these to break ties, not to overrule the item’s own numbers. If you’d like a second opinion mid-game, TFTSense tells you what to slam and who should hold it.

What changes when Set 19 lands?

Riot’s schedule lists 19.1 for December 1, 2026, and warns that dates can change. The shapes here don’t rest on a set: a percentage pays more on a bigger base, a flat amount pays less, and a multiplier holds its value. Re-check the numbers in each table against the 19.1 notes, plus any Riot line on how these stats stack, since one line would settle most of the open questions above.

Sources

All read November 4, 2026. No Riot page was found that prints the Armor or Magic Resist formula or how Durability and Damage Amp sources combine, so those sums are working rules and this guide’s own arithmetic.

• Riot Games, patch 14.16 notes, published 2024-08-13, for the gloss on Durability.
• Riot Games, patch 14.18 notes, published 2024-09-10, for true damage’s limited counterplay.
• Riot Games, patch 14.23 notes, published 2024-11-19, and patch 17.1 notes, published 2026-04-14, for stacking Damage Amp sources and tank items’ multiplicative value.
• Riot Games, patch notes for 18.2 (2026-09-09), 18.3 (2026-09-22), 18.4 (2026-10-06) and 18.5 (2026-10-20), for Golden Dragon, Inferno, Executioner, Damage Amp, Spirit Visage, Crownguard, Juggernaut and Attuned, with 18.6 (2026-11-03) changing none of them.
• Riot Games, Enchanted Wilds Overview, published 2026-07-27, for Burn, and Teamfight Tactics, Enchanted Wilds: Part I, published 2026-08-26, for Inferno’s stacking.
• Riot Games, patch 13.3 notes, published 2025-01-07, for Deathblade’s Damage Amp.
• Riot Games, TFT Dev post, published 2026-11-02, for the True Damage trait, and Patch Schedule, Teamfight Tactics, for the 19.1 date.
• The game’s data files, read November 4, 2026, in a version not yet updated for 18.6, for Steadfast Heart, Radiant Spirit Visage, Striker’s Flail, Titan’s Resolve, Deathblade, Sunder and Shred items, and Burn on items.

Update log

• 2026-11-04: First version.