How this calculation works
Calculate single-event, union, intersection, complement, and repeated-event probabilities. The result is calculated locally in your browser from the visible inputs, and the method below remains available for checking.
Worked example
A 20% event tried three times has a 48.8% chance of occurring at least once.
Assumptions and limits
- Inputs use the units shown beside each field.
- Intermediate values retain precision; displayed values are rounded for readability.
Questions people ask
How does the Probability Calculator work?
It applies this displayed method: Independent intersection = P(A)P(B); union = P(A)+P(B)−P(A)P(B); at least once = 1−(1−P(A))ⁿ. Values stay in your browser and are not submitted to a server.
What should I check before using the Probability result?
Inputs use the units shown beside each field. Intermediate values retain precision; displayed values are rounded for readability. The result follows the displayed mathematical definition and the precision of the values entered.
Does this Probability calculator save my information?
No. Calculation inputs are processed on this device. Sharing creates a URL only when you choose the share action.