Bayes theorem calculator
Enter probabilities as values from 0 to 1.
Branch probabilities
Bars show the calculated outcomes.
Calculation branches
| Event | Probability |
|---|---|
| Fill in the fields above — the result is computed on this page. | |
How do I use this page?
- Enter inputs.
- Check the branches and formula.
What this page does not do: The result assumes the supplied conditional probabilities are correct; repeated-trial mode assumes independence.
Further reading
Theory — what is Bayes' theorem?
Bayes' theorem updates the probability of an event based on new information, such as a test result. The calculator applies the multiplication rule and the complementary event, displaying every intermediate value in the calculation. Inputs must be entered as decimal values between 0 and 1, not as percentages. This makes it possible to see step by step how the initial assumptions translate into the resulting probability.
Frequently asked questions
Can I enter percentages?
See also
A/B test calculator
Compare two proportions in an A/B test. Calculate conversion rates, difference, uplift, z score, p value and c
A/B test planning — sample size, MDE and duration
Plan a two-proportion experiment, estimate detectable effect and traffic duration.
ACF and PACF autocorrelation calculator
Calculate ACF and PACF across time-series lags. Review the chart, reference bounds and coefficient table.