Drop Chance Calculator
Work out your chance of getting a loot drop after any number of kills or attempts, from its drop rate.
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What this tool does
Work out your chance of getting a loot drop after any number of kills or attempts, from its drop rate. Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
How to use the Drop Chance Calculator
- Enter or select drop chance per attempt (%).
- Enter or select attempts (kills, runs, openings).
- Read the calculated result; change any measurement to compare alternatives.
Formula
chance of at least one drop in n attempts = 1 − (1 − p)^n, where p is the per-attempt drop chance; attempts needed for a target confidence = ceil( ln(1 − target) ÷ ln(1 − p) )
- rate
- Drop chance per attempt (%)
- attempts
- Attempts (kills, runs, openings)
Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
Worked example
For drop chance calculator, the following measurements illustrate the exact method: Drop chance per attempt (%): 1; Attempts (kills, runs, openings): 100.
Inputs
- Drop chance per attempt (%)1
- Attempts (kills, runs, openings)100
Result
- Chance of at least one drop (%)63.4
- Expected attempts per drop100
- Attempts for 50% confidence69
- Attempts for 90% confidence230
- Attempts for 95% confidence299
- Attempts for 99% confidence459
Results explained
- Chance of at least one drop (%)
- Chance of at least one drop (%) from the formula above. Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
- Expected attempts per drop
- Expected attempts per drop from the formula above. Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
- Attempts for 50% confidence
- Attempts for 50% confidence from the formula above. Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
- Attempts for 90% confidence
- Attempts for 90% confidence from the formula above. Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
- Attempts for 95% confidence
- Attempts for 95% confidence from the formula above. Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
- Attempts for 99% confidence
- Attempts for 99% confidence from the formula above. Assumes every attempt is independent with the same drop chance and no pity timer, bad-luck protection or lockout — games with those systems will drop sooner than this model predicts.
Frequently asked questions
No. After 100 attempts at 1% you have only about a 63.4% chance of having seen it. Roughly 37% of players go 100+ dry — that's how independent probability works, and why 'expected attempts' is an average, not a promise.
299 kills: 1 − 0.99^n ≥ 0.95 first holds at n = 299. The 99% mark needs 458. Long tails are the nature of geometric probability.
For a geometric distribution the mean wait is exactly 1/p: a 2% drop averages 50 attempts. But the median wait is shorter (~35), because a few very unlucky streaks drag the mean up.
Not under this model — each attempt is independent, so past failures don't raise the next attempt's chance. If your game has a pity system, your real odds improve faster than shown here.
Enter it as a percent: 1 ÷ 500 = 0.2%. The calculator accepts decimal percentages, so 0.2 in the drop-chance field is right.