Loot Drop Probability Calculator
Find the chance of getting a rare drop over repeated attempts, the expected number, and how many tries reach a 50, 90 or 99 percent chance. Calculates in your browser.
Chance of at least one drop
-
Show the math
Each attempt is independent, so the chance of seeing at least one drop is one minus the chance of missing every time:
P(≥1) = 1 − (1 − p)ⁿ
Note the expected count can exceed one without a guarantee, even with an "average" of one drop, you'll come up empty about 37% of the time.
All math runs locally in your browser.
What this does
A loot drop probability calculator finds the chance of getting a rare drop over repeated attempts, the expected number, and how many tries reach a 50, 90, or 99 percent chance.
How to use it
- Enter the drop rate.
- Enter the number of attempts.
- Read the at-least-one chance.
- See the tries for 50/90/99%.
How it works
Each attempt is independent, so the chance is one minus the probability of missing every time. An expected count of one still misses about 37% of the time.
P(at least one) = 1 − (1 − rate)^attempts
Understanding your result
The key reality check is that an expected count of one is not a guarantee, with independent rolls you still miss about 37 percent of the time after the average number of tries. That is why the tool also shows the attempts needed for 50, 90, and 99 percent confidence: plan around the 90 percent figure if you want to be reasonably sure of the drop.
Example
A 1% drop has about a 63% chance after 100 tries.
Sources & methodology
Last updated .
Frequently asked questions
How is the at-least-one chance found?
Each attempt is independent, so the chance is one minus the probability of missing every single time.
Does an expected count of one mean a guarantee?
No. Even when the average is one drop, you will come up empty about 37 percent of the time.
Is my data kept?
No. Everything is computed locally in your browser.
Related tools
DPS Calculator
Work out damage per second from your hit damage, attack speed, critical chance and critical multiplier, with average damage per hit and per minute. Calculates in your browser.
Gacha Probability Calculator
Estimate your chance of pulling a featured item from the pull rate and number of pulls, including a hard-pity guarantee. Calculates in your browser.
Elo & MMR Calculator
See your new rating after a match from your rating, the opponent’s rating and the result, with the expected score and a tunable K-factor. Calculates in your browser.
Speedrun Timer
Paste your splits to get segment times, the sum of your best segments, and the theoretical best-possible run, plus the time you could save. Calculates in your browser.