League of Legends Damage Calculator
Work out the real damage an attack deals in League of Legends after armor or magic resist. Enter raw damage and resist to see damage taken and reduction percent.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Enter the raw damage of an attack and the target's armor (for physical) or magic resist (for magic). Uses the standard League of Legends resistance formula.
Show the formula & steps
How the League of Legends Damage Calculator Works
In League of Legends, the damage number on an ability or attack is the raw value before defenses. The amount a target actually loses depends on its armor (for physical damage) or magic resist (for magic damage). This calculator applies the game’s standard resistance formula so you can see the true damage taken, how much was reduced, and the effective reduction percent.
Enter the raw damage of the attack and the target’s resist for that damage type. Reduce the resist by any penetration the attacker has first.
The Formula
For non-negative resist, League uses:
Damage multiplier = 100 / (100 + resist) Damage taken = raw damage × damage multiplier Reduction % = (1 - damage multiplier) × 100
When resist is negative (after shred or reduction), damage is amplified instead:
Damage multiplier = 2 - 100 / (100 - resist)
This curve means resist has diminishing percentage returns but linear effective-health returns. Every point of armor or magic resist makes your health pool worth more against that damage type.
Worked Example
A spell deals 500 raw magic damage to a target with 100 magic resist:
- Multiplier = 100 / (100 + 100) = 100 / 200 = 0.5
- Damage taken = 500 × 0.5 = 250
- Reduced = 500 - 250 = 250 (a 50 percent reduction)
If the same target had 0 magic resist, the multiplier would be 100 / 100 = 1.0, so it would take the full 500 damage.
Resist vs. Reduction at a Glance
The relationship between resist and reduction is a smooth curve, not a straight line:
| Armor / magic resist | Damage multiplier | Reduction % | Effective health gain |
|---|---|---|---|
| 0 | 1.000 | 0% | +0% |
| 50 | 0.667 | 33.3% | +50% |
| 100 | 0.500 | 50.0% | +100% |
| 200 | 0.333 | 66.7% | +200% |
| 300 | 0.250 | 75.0% | +300% |
Why This Matters for Builds
Because each point of resist adds the same amount of effective health, defenses pair best with raw health. Buying only resist or only health leaves value on the table; combining them multiplies survivability. Attackers respond with penetration, which lowers the target’s resist for their damage and tilts the trade back. Run your numbers through the calculator before and after penetration to see how much a defensive or offensive item really changes a fight.
Frequently asked questions
How does armor reduce damage in League of Legends?+
Armor uses the formula damage multiplier = 100 / (100 + armor). At 100 armor the multiplier is 100/200 = 0.5, so you take half damage, which is a 50 percent reduction. Magic resist works identically against magic damage.
Does 100 armor mean 100 percent damage reduction?+
No. Armor and magic resist scale by a curve, not a flat percentage. 100 armor gives 50 percent reduction, 200 armor gives about 66.7 percent, and 300 armor gives 75 percent. Each point of resist adds slightly less reduction than the last, but it always increases your effective health.
What happens when armor or magic resist is negative?+
Negative resist amplifies incoming damage. The game switches to multiplier = 2 - 100 / (100 - resist). At -100 armor the multiplier is about 1.5, so the target takes 50 percent extra damage. Shred and reduction effects can push resist below zero.
Should I subtract penetration before using this calculator?+
Yes. Apply the attacker's flat and percentage penetration to the target's resist first, then enter the reduced value here. Penetration lowers effective resist for that source of damage but never below zero from percentage penetration alone.
Why is stacking resist called effective health?+
Because resist multiplies how much raw damage your health can absorb. At 100 armor your health blocks twice the physical damage, so 2000 health behaves like 4000 effective health against physical attacks. This is why tanks buy both health and resistances.