Gaming math lab · Combat · Original calculator
Effective health and damage reduction calculator
On this page
With multiplicative reductions, multiply the fractions of damage remaining. Effective health is health divided by that remaining fraction.
Generic mathematical model, not a named game’s simulator. All starting values are invented examples. Supply verified values for your game and check the assumptions below.
Your scenario
Formula and units
Remaining damage fraction = (1 − A) × (1 − B). Combined reduction = 1 − remaining fraction. Effective health = health / remaining fraction.
Worked example
At 1,000 health with reductions of 20% and 30%, the remaining damage fraction is 0.8 × 0.7 = 0.56. Combined reduction is 44%, not 50%. Effective health is 1,000 / 0.56, approximately 1,785.714 incoming damage.
How to use this comparison
First identify the damage type you want to compare. Enter a verified reduction percentage rather than an armour stat whose conversion you do not know. Leave a layer at zero if it does not apply. The table separates no mitigation, layer A alone and both layers.
Read the result correctly
Effective health is a capacity for absorbing incoming damage in this specific model. A larger health pool and a mitigation increase can be compared only when the same damage type and conditions apply. A displayed improvement does not establish survival against mechanics that bypass the reductions.
Model boundaries
The two layers must actually stack multiplicatively for the incoming damage type. This is not an armour-rating conversion formula. It excludes shields, healing, flat damage subtraction, penetration, dodge and damage-over-time interactions. A 100% reduction has no finite result here and is rejected.
Method: original arithmetic implementation and editorial examples reviewed October 16, 2026. Outputs follow the displayed formula and your inputs. We have not tested these mechanics inside a particular game.