Effective HP is the raw damage needed to kill a target once its mitigation is counted: EHP = HP ÷ (1 − reduction). With the common armor formula, reduction = armor ÷ (100 + armor), so EHP = HP × (1 + armor ÷ 100). A champion with 1,000 HP and 100 armor has 2,000 effective HP against physical damage.
Build planners, theorycrafters and players comparing defensive items all run into the same question: is another 300 health worth more than 40 armor? Effective HP answers it by folding mitigation into one number, the amount of unmitigated damage an enemy must deal before the health bar empties. Enter health, then pick whether your game reports defence as an armor-style stat (League of Legends, Dota-like formulas using 100 as the constant) or as a straight damage-reduction percentage. The result shows the EHP, the reduction it implies, the multiplier on your health and how much extra damage the mitigation soaks. One limit: the armor option assumes the A ÷ (100 + A) curve; games with other constants, penetration, flat block or shields need those applied before you enter the numbers.
Type the current maximum health pool of the character or unit.
Choose armor or resist value for stat-based games, or reduction percent if the game shows a percentage.
Enter the armor value, or drag the slider to the damage reduction percentage.
Compare the EHP, the multiplier and the extra damage absorbed between two builds.
Result Effective HP: 2,000
Damage reduction: 50%
EHP multiplier: 2
Extra damage absorbed: 1,000
At 100 armor half of each hit is blocked, so the champion survives twice the raw damage.
Result Effective HP: 4,000
Damage reduction: 75%
EHP multiplier: 4
Extra damage absorbed: 3,000
Taking a quarter of each hit means four times the raw health must be dealt before the bar empties.
Result Effective HP: 3,750
Damage reduction: 33.33%
EHP multiplier: 1.5
Extra damage absorbed: 1,250
50 armor blocks a third of physical damage, adding 1,250 effective health.
EHP = HP ÷ (1 − R), with R = A ÷ (100 + A) for armor, which simplifies to EHP = HP × (1 + A ÷ 100)
HPAREHPIf a fraction R of each hit is blocked, only 1 − R of it reaches health, so the attacker must deal HP ÷ (1 − R) raw damage. Under the armor curve each point of armor adds exactly 1% of base health as effective health, which is why armor never shows diminishing returns per point of EHP even though the reduction percentage flattens out.
The reduction percentage does: 100 armor blocks 50%, 200 blocks 66.7%, 300 blocks 75%. Effective health does not, because each point still adds 1% of base health as EHP. Against that, health and armor multiply each other, so the best value comes from keeping the two balanced.
Multiply the damage taken. A 20% reduction plus a 30% reduction lets through 0.8 × 0.7 = 0.56 of the damage, a combined 44% reduction, not 50%. Enter 44 in the reduction slider.
Compare EHP per gold. Under the armor curve, one armor adds 1% of current health as EHP, and one health adds (1 + armor ÷ 100) EHP. When health is much more than 100 × (gold per armor ÷ gold per health) times the armor, armor is the better buy, and the other way round.
It is how many points of raw damage it takes to remove one point of health. A multiplier of 2 means every hit is halved, so your bar lasts twice as long against that damage type.
At 100% reduction effective health becomes infinite, which no game allows. Close to that cap the number rises very steeply, so small rounding in the game's tooltip can change EHP by thousands.
Some games let shred push armor below zero, which increases damage taken. This calculator accepts zero and above only; for negative armor, find the game's own amplification rule first.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 16). EHP Calculator. Tools Directory. Retrieved October 26, 2026, from https://tools.milunir.com/gaming/damage-and-combat-stats/ehp-calculator/
Tools Directory Editorial Team. “EHP Calculator.” Tools Directory, 16 Oct. 2026, https://tools.milunir.com/gaming/damage-and-combat-stats/ehp-calculator/. Accessed 26 Oct. 2026.
Tools Directory Editorial Team. “EHP Calculator.” Tools Directory. Last modified October 16, 2026. Accessed October 26, 2026. https://tools.milunir.com/gaming/damage-and-combat-stats/ehp-calculator/.
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