Drop Rate Probability Calculator
Works out your chance of a drop over many attempts.
Chance of at least one drop
— %
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Chance of none — %
Average number of drops —
Average attempts per drop —
Reading this —
The formula
chance of at least one = 1 − (1 − rate)^attempts
It is easier to work out the chance of getting none, then take it from 1.
What to watch out for
Past failures do not make the next attempt more likely under independent rolls. Doing as many attempts as the 1-in-X figure gives only about 63%.
Frequently Asked Questions
What is the chance of a 1% drop in 100 attempts?
63.40%, not 100%.
Does a 1-in-100 drop always come within 100 tries?
No. There is a 36.60% chance of none.