Armour maths: why 20 armour points is not 80% reduction
The armour formula includes toughness and the attack's armour-piercing. Here is the real equation, what Protection adds on top, and where the hard caps sit.
Full diamond armour shows 20 points — ten icons — and people read that as 80% damage reduction. The real number depends on how hard you were hit.
The formula
reduction = min(20, max(armour/5, armour − damage/(2 + toughness/4))) × 4%Two things fall out of it:
- Armour gets worse against big hits. The
damage/(2 + toughness/4)term subtracts
more as incoming damage rises. Against a 2-damage zombie punch, 20 armour is near its cap. Against a 40-damage explosion, much less.
armour/5is a floor. No matter how large the hit, you keep at least a fifth of
your armour value in effect — 20 armour never drops below 4 points, or 16%.
Toughness only appears in that subtraction, which is exactly why it matters against heavy hits and does nothing against weak ones. Diamond has 2 per piece, netherite 3. That difference is invisible against a zombie and real against a charged creeper.
Protection stacks separately, and after
Enchantment protection is a second, independent reduction applied to what armour left:
EPF total (capped at 20) × 4% → up to 80% of the remainderProtection IV on four pieces gives EPF 16, so 64%. Combined with a full armour reduction, total mitigation approaches — but never reaches — 96%. There is always a floor.
Specialised protections (Blast, Fire, Projectile) count double against their damage type but nothing otherwise, so a Blast IV set is stronger than Protection IV against creepers and weaker against everything else.
Damage types that ignore armour
Armour does nothing against:
- Fall damage — Feather Falling only
- Drowning, starvation, suffocation
- The void
- Poison and Wither — status effects, not hits
/killanddamage_typeentries flagged as bypassing armour
This is why a fully-armoured player still dies to a long fall, and why Feather Falling IV is worth more than the same enchantment slot spent on Protection for anyone who uses an Elytra.
Resistance is multiplicative on top
Resistance reduces by 20% per level, applied after everything else, and it does work against most of the bypass types above. Resistance V — only reachable via commands or a beacon plus effects — is total immunity.
Practical takeaway
- Netherite over diamond matters against explosions and heavy hits, not against mobs.
- Protection IV beats specialised protections unless you know exactly what will hit you.
- Above roughly 20 armour points nothing improves; the cap is real.
- Against very large single hits, health and Resistance matter far more than armour.
Run your own numbers, including toughness and enchantments, in Reference & Calculators — Set 2.