Calculate probabilities for two independent events: both, either, neither, exactly one and not A. Enter your values; the result updates as you type, with the method shown below.
Formula
P(A ∩ B) = P(A) × P(B) P(A ∪ B) = P(A) + P(B) − P(A ∩ B)
Worked example
P(A) = 50%, P(B) = 30%: both 15%, either 65%.
Frequently asked questions
What are independent events?
Events where one does not affect the other, like two coin flips.
Why is P(A or B) not just the sum?
You must subtract the overlap counted twice.
Can I use decimals?
Enter percentages from 0 to 100.
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Results are estimates for information only. Check important figures with a professional.