Bayes' Theorem Calculator

Calculate conditional probabilities and update beliefs with evidence

Pre-loaded Examples

Medical Testing

Disease prevalence 1%, test sensitivity 95%, specificity 90%

Spam Filter

30% spam rate, keyword "FREE" in 60% of spam, 5% of legitimate email

Airport Security

0.001% threat rate, scanner 99% accurate, 10% false positive

Input Probabilities

Prior P(A)

Initial probability of event A

0.010

Likelihood P(B|A)

Probability of B given A is true

0.950

P(B|¬A)

Probability of B given A is false

0.100

Labels (Optional)