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Drop chance math: how multipliers actually stack

What happens when you stack +30% from a rune, +15% from gear and +10% from a buff. Multiplicative vs. additive.

QUICK GUIDE
  • Same-source bonuses stack additively. Cross-source bonuses stack multiplicatively.
  • Three +30% runes ≠ +90%. They go on three separate nodes that may all feed the same final stat — check before you spend.
  • Gear mods, rune nodes and buffs sit in different stacking buckets. Mixing buckets gives the biggest gains.
  • Past about +200% total drop chance, marginal value starts dropping — diversify into Chest Cap and Auto-Open Speed.
  • Same-source vs cross-source

Same-source vs cross-source

Inside one source (e.g. all your rune nodes contributing to Drop Chance Normal Chest), bonuses add: 10% + 7% + 7% = 24%. Across sources (rune total × gear mod × consumable buff), they multiply: 1.24 × 1.15 × 1.10 = ~1.57, or +57% effective.

The three buckets

  • Rune bucket — permanent. Roughly +5% to +20% per node, additive within itself.
  • Gear bucket — temporary while equipped. +Drop Chance rolls on accessories.
  • Buff bucket — temporary timed buffs from items/events.

Diminishing returns

Drop Chance has a soft cap in the sense that you can only open chests as fast as your Auto-Open timer allows. Past about +200% combined drop chance, your bottleneck flips from "do I get a chest" to "can I open them fast enough". At that point, invest in Rune of Lubrication (reduce auto-open time) and Rune of Containment (max chest cap) instead of more drop chance.

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