Effective HP (EHP) Calculator
True survivability from raw HP plus damage reduction (armor/resist) — why 50% reduction doubles your effective health.
Damage reduction divides incoming damage, so EHP = HP/(1−DR). At 50% reduction you survive twice the damage; at 75%, four times. This convexity means stacking armor has INCREASING returns against pure damage — the opposite of the 'diminishing returns' most players assume.
Formula
About Effective HP (EHP) Calculator
A health bar lies about survivability. What keeps a character alive is effective HP — raw health divided by the fraction of damage that gets through, EHP = HP / (1 − reduction). This calculator reveals the counter-intuitive convexity of damage reduction: going from 0% to 50% reduction doubles your effective health, and 50% to 75% doubles it again. That means each point of armor is worth MORE as you stack it (against raw damage), which is why tank itemization and the armor-vs-HP decision are central balance problems this tool makes concrete.
How to use Effective HP (EHP) Calculator
- 1Enter your values into Effective HP (EHP) Calculator — sensible, domain-typical defaults are pre-filled so you see a real result immediately.
- 2The result recomputes live using the formula shown on the page; there is no button to press.
- 3Adjust any input to compare scenarios, then read the worked example to see the substituted numbers.
Why use Effective HP (EHP) Calculator?
- ✓Computes Effective HP (EHP) instantly in your browser — no sign-up, no upload, no server round-trip.
- ✓100% free and unlimited, with the exact formula shown: EHP = HP / (1 − damageReduction) — reduction multiplies effective health; this is why each point of armor is worth MORE .
- ✓Runs entirely client-side, so every value you enter stays private on your device.
- ✓Live recompute as you type, with a worked example and authoritative references for trust.
Frequently asked questions
Why does damage reduction give increasing returns?+
Because it divides incoming damage rather than subtracting flat health. EHP = HP/(1−DR), and 1/(1−DR) grows faster as DR rises: 0→50% is a 2× gain, 50→75% another 2×, 75→87.5% another. Each percentage point of reduction is worth more EHP than the last — the opposite of the diminishing-returns intuition most players have.
Armor or raw HP — which should I stack?+
They're multiplicative, so balance them. EHP = HP × multiplier, and the product is maximized when you invest in both rather than maxing one. Pure reduction with low HP shatters to true/percent-max-health damage; pure HP with no reduction takes full hits. Optimal tankiness stacks them together — exactly why this tool shows both factors.
How do designers stop armor from being overpowered?+
Several levers: diminishing returns on the armor→reduction conversion (common — armor gives less reduction as it grows, flattening the EHP convexity), armor penetration on attackers, percent-max-health and true damage that bypass reduction, and hard reduction caps. Without these, the EHP math here would make stacked armor unkillable.
Does EHP account for healing and regeneration?+
Not directly — EHP measures the damage you can absorb in one burst. But reduction also multiplies the value of healing: at 50% reduction, every point healed effectively restores 2 EHP. So defensive layers and sustain compound, which is why reduction-stacked tanks with healing are disproportionately durable. Model sustain separately on top of the EHP here.
Related Game Dev tools
DPS (Damage Per Second) Calculator
Effective DPS from hit damage, attack speed, crit chance and crit multiplier — the core combat-balance number.
● LiveDrop Rate / Expected Tries Calculator
Probability of at least one drop in N tries, expected tries to get one, and the 'pity' attempt count.
● LiveXP Curve & Level Cost Calculator
XP required for a level and total cumulative XP under linear, polynomial or exponential progression curves.
● Live