Measure

Effective health

You might say: EHP, effective HP, effective health pool, physical EHP

Effective health is the unmitigated damage required to defeat a target after mitigation. For damage = attack × K/(K + armour), EHP = health × (1 + armour/K) before discrete minimum-damage and rounding caveats.

What it does

Puts health and armour on one survivability scale for comparing defenders and checking whether the armour curve gives the intended durability.

Ask

How much raw damage does this defender survive, and does that prediction still match discrete HTK against each attacker?

Typical

EHP = H/(K/(K + A)) = H(1 + A/K) for nonnegative divisive armour; recalculate per damage type and condition

Trouble

Treating EHP as universal despite flat reduction, minimum damage, rounding, shields, cover, flanking, penetration or mixed damage; EHP may not predict exact HTK.

Connections

• See also: Interaction formula catalogue
• See also: Time-to-kill
• See also: Hits-to-kill matrix

Sources

1. League of Legends Wiki, Armor, Armor formula; effective health; Stacking armorThe second formula proves that armor increases nominal health by a percentage against physical damage; this is called effective health.
2. StatGarden, Effective HP calculator from armour rating, What this calculator does; Formula; Worked examples; QuestionsFormula damage reduction = armour ÷ (armour + K); effective HP = health ÷ (1 − damage reduction) = health × (1 + armour ÷ K)
3. Blizzard, Warcraft III Armor and Weapon Types, Damage Reduction or Increases for ArmorA unit with 20 armor basically has 55% extra hitpoints -- 100 would become effectively 155.
4. Calc, Hits to Kill Calculator, Formula; Effective HP; Frequently askedEffective HP = HP ÷ (1 − reduction%); 50% reduction doubles the hits required.
5. GameDesign.gg, Weapon Design: The Feel, Math, and Balance of Guns, The Core Numbers: Damage, Fire Rate, and Time-to-KillShots to kill is the enemy’s effective health divided by damage per shot, rounded up.

Unverified: The linear EHP expression is exact for this divisive ratio before minimum-damage and rounding; flat mitigation, shields and mixed damage require a specified incoming profile.

Use it on your project

teardown-apply: hold "Effective health" (htk-effective-health) from the teardown at https://teardownatlas.com/game-design/ against my project

Paste it into a coding agent that has the teardown skills.

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