Effective Health (EHP) Calculator

How this is calculated

Effective health is your health divided by (1 minus your damage reduction). At 40 percent reduction you take 60 percent of incoming damage, so your health goes 1 divided by 0.6 times as far - about 1.67 times. The important property is that this is NOT linear. Each additional point of damage reduction is worth more than the one before it, and the effect accelerates sharply near the top: At 5000 health, going from 40 to 50 percent reduction adds about 1,667 effective health. Going from 80 to 90 percent adds 25,000 - fifteen times as much for the same ten points. At 90 percent you have ten times your health bar; at 95 percent, twenty times. The reason is that what matters is not how much damage you block but how much gets THROUGH. Going from 80 to 90 percent reduction does not block 12 percent more - it HALVES what reaches you, from 20 percent down to 10. Reduction stacking is really a race to shrink the leftover, and every step you take makes the next one worth more. This has a practical consequence worth knowing: stacking resistance has increasing returns while stacking raw health has flat ones, so the two are usually best bought together rather than one at a time. Health with no reduction is fragile and reduction with no health has nothing to multiply. ⚠️ The damage reduction box wants your FINAL reduction percentage, not an armour or resistance rating. Almost every game converts armour to a percentage through its own curve, and those curves differ wildly - many have diminishing returns built into the conversion itself, which partly offsets the increasing returns described above. Read the percentage off your character sheet rather than the raw stat. Not modelled: damage types with separate resistances, flat damage reduction that subtracts rather than scales, shields and absorbs, healing, dodge and block chance, and any cap your game places on resistance. Treat this as a comparison tool for two builds, exactly as with DPS.

Common questions

Why is 10% more reduction worth so much more at 80% than at 40%?

Because what matters is not what you block, it is what gets THROUGH. Going from 80 to 90 percent does not block 12 percent more - it halves the damage reaching you, from 20 percent down to 10, which doubles your effective health. Going from 40 to 50 percent only cuts the leftover from 60 to 50, which is a much smaller proportional change. At 5000 health those two identical-looking upgrades are worth 25,000 and 1,667 effective health respectively.

So should I stack reduction over health?

Usually together rather than either alone. Reduction has increasing returns and raw health has flat ones, which sounds like an argument for reduction - but reduction multiplies your health, so with a small health pool there is little to multiply. The extreme of either is bad: enormous health with no reduction is fragile against big hits, and enormous reduction on a tiny pool still dies to anything that ignores it.

My game shows armour, not a percentage. What do I enter?

Find the percentage on your character sheet - most games display the converted figure somewhere, and that is what this wants. Armour ratings go through a conversion curve that differs completely between games, and many of those curves have diminishing returns built in, which partly cancels the increasing returns described here. Entering a raw armour number as if it were a percentage will produce nonsense.

Does this account for dodge or block?

No. Avoidance is a different mechanic - it removes a proportion of hits entirely rather than shrinking every hit, and it is random rather than reliable, which matters a great deal for whether a healer can keep up with you. Averaged over a long fight avoidance behaves a bit like reduction; over a three-second burst it does not, which is exactly when tanks die.

What about a resistance cap?

Many games cap reduction, often somewhere between 70 and 90 percent, precisely because the maths here runs away otherwise. The input stops at 95 percent for the same reason - at 100 percent effective health is infinite, which is not a number any game intends. If your game has a cap, points past it are worth nothing at all, which is the sharpest possible case of a stat losing value.

Why does the hits-survived figure round up?

Because the hit that takes you from a sliver of health to zero still counts as a hit you did not survive but did take. Four and a bit hits means the fifth kills you, and the fifth is the one worth planning around. It is deliberately the pessimistic reading.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Effective Health (EHP) Calculator at https://www.bfcbrilliance.com/tools/effective-health-calculator.

What I entered:
- Health: ___
- Damage reduction (%): ___
- Incoming hit (before reduction): ___

What it calculated:
- Effective health: ___
- Your health goes this much further: ___
- That hit actually deals: ___
- Hits you survive: ___
- Ten more points of reduction would add: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

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