How to use it
- Enter the probability of events A and B as percentages.
- Select independent events when one event does not affect the other.
- For dependent events, provide the known intersection before calculating.
Probability Calculator
Calculate combined and complementary probabilities for two events.
About the Probability Calculator
Use two event probabilities to find the chance that both occur, at least one occurs, or an event does not occur.
Probability rules
For independent events, P(A and B) equals P(A) multiplied by P(B). The union is P(A) plus P(B) minus P(A and B), and a complement is 1 minus the event probability.
Independent versus dependent
Two coin flips are independent, while drawing two cards without replacement is dependent. Use a known intersection for dependent events because multiplying the two probabilities is not generally valid.
Example
If independent events have probabilities of 40% and 50%, both occur with probability 20%, while at least one occurs with probability 70%.