Drop rate & loot odds calculator
Work out your chance of getting at least one drop across multiple attempts, or how many attempts you'd need for a target chance.
This is an estimate based on the rate you enter — it's not a guarantee, and it doesn't model pity/bad-luck-protection systems.
This calculator doesn't look up or store any game's actual drop tables — you supply the rate, from the game's own published numbers or a community wiki. That's deliberate: a formula never goes stale from a balance patch the way a stored drop-rate table would.
Worked example
Say an item has a 2% drop rate per attempt, and you make 50 attempts. 1 − (1 − 0.02)^50 ≈ 63.6% — roughly a two-in-three chance of at least one drop across those 50 tries.
Want to be 90% confident instead? At the same 2% rate, that takes about 114 attempts — considerably more than 50, since pushing confidence from "likely" to "near-certain" costs a lot more tries than the jump from zero to "likely" did.
FAQ
How is the cumulative drop chance calculated?
Standard binomial probability: 1 minus the chance of missing every single attempt, or 1 − (1 − drop rate)^attempts.
Where do I find the drop rate to enter?
This calculator doesn't look up any game's drop tables — enter the rate as published by the game's developer or community wiki for the specific item you're after.
Does this account for pity systems or bad-luck protection?
No — this is a plain independent-attempt calculation. Games with a pity/soft-pity system (common in gacha games) behave differently once you're close to the pity threshold; that's a separate, more specific calculator.
My drop rate is a fraction, like 1-in-4 — how do I enter it?
Convert it to a percentage first: 1-in-4 is 25, not 0.25 or 4. The field expects a number between 0 and 100.
What happens if I enter a drop rate over 100%?
It's rejected as invalid rather than being capped at 100% automatically — a rate above 100% isn't a meaningful percentage.
For a low target confidence, do I need more attempts or fewer?
Fewer — a low target (say 10%) needs only a handful of attempts, while a high target (say 99%) needs many more. A lower bar to clear takes less effort, not more.
Does the drop rate stay the same across attempts?
Yes — the calculator assumes a fixed rate for every attempt. It can't model a rate that changes based on how many times you've already tried (which is what a pity system does).
Can I use this for board games or other non-video-game probability?
The underlying math (binomial probability) applies broadly, but it's built and worded for game drop rates specifically.
How accurate is the result?
It's exactly as accurate as the drop rate you enter — the calculator itself does the arithmetic precisely, but real-world outcomes will still vary randomly around the estimate.