Work out loot drop probability instantly with clear inputs, formula shown and shareable results.
Independent attempts follow the geometric distribution: the chance of no drop is (1 - rate) to the power of attempts, and the attempts for a 90% chance is log(0.1) over log(1 - rate). At a 2% rate the average is 50 attempts but 115 are needed for a 90% chance, which is why runs of bad luck feel far worse than the headline rate suggests.
At least one drop
P = 1 - (1 - drop rate) ^ attempts
Attempts for 90%
attempts = ln(0.1) / ln(1 - drop rate)
P = 1 - (1 - drop rate) ^ attempts. Independent attempts follow the geometric distribution: the chance of no drop is (1 - rate) to the power of attempts, and the attempts for a 90% chance is log(0.1) over log(1 - rate).
At a 2% rate the average is 50 attempts but 115 are needed for a 90% chance, which is why runs of bad luck feel far worse than the headline rate suggests.
Enter drop rate per attempt, attempts made. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.