Bayes' Theorem Calculator

Update probability of (name of event A)
based on (name of event B)
P() = (prior probability of )
P(|) = (probability of given )
P(|¬) = (probability of given ¬)
P(|) = (posterior probability of given )
P(|¬) = (posterior probability of given ¬)

Load example

Usage notes

Both decimal and % probabilities are supported.

This uses BigDecimal, not floating point math. It still loses bits with non-terminating decimals, though.

If you rely on this, save a local copy of this page with ctrl+s or ⌘+s. The JavaScript will probably work fine in your local copy.

No warranty of any kind; see this fearsome no-warranty clause.

Bugs? and please mention your browser version.