Probability Calculator
Find P(A or B), conditional probabilities and independence. The result updates as you type, with the working underneath so you can check it.
Your details
Result
P(A or B)
0.7000
- P(A and B)
- 0.2000
- P(A | B)
- 0.4000
- P(B | A)
- 0.5000
- Independent?
- Yes
- Neither occurs
- 0.3000
Good to know: P(A or B) = P(A) + P(B) − P(A and B)
About this tool
Formula
P(A or B) = P(A) + P(B) − P(A and B)
Questions people ask
How do I know if events are independent?
A and B are independent if P(A and B) = P(A) × P(B).
Related tools
- Z-Score CalculatorFind how many standard deviations a value is from the mean, with percentile.
- Normal Distribution CalculatorFind probabilities for a normal distribution.
- Binomial Distribution CalculatorFind the probability of exactly or at most k successes in n trials.
- Confidence Interval CalculatorFind the confidence interval for a mean from the sample mean, standard deviation and size.
How we calculate this
We use the standard published formula or definition for this calculation, and we show the working so you can check it.
Spotted a mistake? Tell us and we'll check it. How we check our calculators