How to use it
- Enter the published chance for one attempt.
- Enter how many independent attempts you plan to compare.
- Calculate the chance of at least one drop and the expected count.
Drop Rate Calculator
Estimate the chance of at least one drop across repeated independent attempts.
About the Drop Rate Calculator
A per-attempt drop rate does not directly equal the chance of success after several tries; repeated attempts compound the probability.
Probability formula
The chance of at least one drop is 1 - (1 - p)^n, where p is the chance per attempt and n is the number of attempts.
Example
A 1% independent chance repeated 100 times gives about a 63.4% chance of at least one drop, not a guarantee.
Notes
The calculation assumes every attempt is independent and uses the same rate. Pity systems or changing rates require different rules.