Drop Chance Calculator
Work out the real chance of a 1-in-N loot drop in a number of tries, the tries for a 50%, 90% or 99% chance, and the odds of several drops. Exact maths.
Chance
- Tries for a 50% chance
- 69
- For 90%
- 230
- For 99%
- 459
- Drops expected
- 1
- Each try is independent: at least one drop = 1 − (1 − chance)^tries. Tries for a chance q = ln(1 − q) ÷ ln(1 − chance), rounded up.
- A 1-in-100 drop does not arrive by try 100: by then the chance is only about 63.40%. Bad luck has no memory either — 200 dry tries do not make the next one likelier.
- Games with pity timers or guaranteed drops after a number of tries do not follow this: their rules change the odds.
Drop
How is this calculated?
At least one drop in n tries = 1 − (1 − p)^n. Tries for a chance q = ⌈ln(1 − q) ÷ ln(1 − p)⌉. At least k drops = 1 − Σ (i = 0 to k − 1) C(n, i) pⁱ (1 − p)ⁿ⁻ⁱ.Runs in your browser — nothing you enter leaves this device.
About this tool
What it does
Drop Chance Calculator answers the question every player asks after a long run of bad luck: with a 1-in-N drop, what were my real chances? Enter the drop chance per try — as 1/500, 1 in 500, 0.2% or 0.002 — and the number of tries. It gives the chance of at least one drop, the chance of none, the number of drops you would expect on average, and the tries you need for a 50%, 90% or 99% chance of seeing it. Set “Drops wanted” to see the odds of getting several. The results surprise most people: a 1-in-100 drop is only about 63% likely in 100 tries, a quarter of players are still waiting at 138 tries, and one in ten at 230. Each try is independent — a long dry run does not make the next try likelier. The maths is done with logarithms, so even one-in-a-million chances over millions of tries are exact.
How to use it
- Enter the drop chance per try, in any form.
- Enter the number of tries.
- Optionally set how many drops you want.
- Read the chance and the tries for 50%, 90% and 99%.
Limits and your data
- It assumes every try is independent with the same chance; pity timers, bad-luck protection and guaranteed drops change the odds.
- Published drop rates are sometimes rounded or community estimates.
- Everything is worked out in your browser. Nothing is sent anywhere.
Questions
If a drop is 1 in 100, will I get it in 100 tries?
Only about 63% of the time. For a 90% chance you need 230 tries; for 99%, 459.
Does bad luck build up?
No. Unless the game has a pity system, every try has the same chance, whatever happened before.
How many drops should I expect?
Chance × tries on average: 0.5 drops in 50 tries of a 1-in-100, though most runs give 0 or 1.
Can it work out the chance of two drops?
Yes: set Drops wanted to 2 (or more).