Overview
What Is a Probability Calculator?
This tool calculates the probability of an event occurring, plus combined probability for two independent events (both happening, or either happening).
Calculate probability of single and combined events.
This tool calculates the probability of an event occurring, plus combined probability for two independent events (both happening, or either happening).
Useful for coursework, games of chance, and basic risk assessment.
Input the number of favorable outcomes and total possible outcomes for Event A.
For combined probability, enter Event B's outcomes too.
Individual and combined probabilities update automatically.
Probability = Favorable Outcomes ÷ Total Possible Outcomes.
It means the outcome of one event has no effect on the probability of the other, like flipping two separate coins.
Multiply the individual probabilities of independent events: P(A and B) = P(A) × P(B).
For independent events: P(A or B) = P(A) + P(B) - P(A and B).
No, probability is always between 0 and 1 (or 0% and 100%).
It means the event is certain to happen.
It means the event is impossible.
No, this calculator assumes independence - dependent events require conditional probability, which isn't calculated here.
No, calculations happen entirely in your browser.
Yes, completely free with no sign-up required.