How to use Conditional Probability Calculator
- Choose joint-event calculation or Bayes update.
- Enter probabilities from zero through one.
- Review the numerator, denominator and resulting conditional probability.
Example: Conditional Probability Calculator
Conditional Probability Calculator: P(A given B) = 0.4.
Options
- Joint-event mode
- Divide the entered P(A and B) by P(B). The joint probability cannot exceed the conditioning probability.
- Bayes inputs
- Enter the prior and the likelihood of the evidence under both alternatives. These inputs are assumptions supplied by you.
Supported inputs and limits
Where your input is processed
This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.
Reverse conditional probabilities are different questions
P(B given A) is not usually P(A given B). The prior and alternative likelihood affect the Bayes result. A zero conditioning probability makes the ratio undefined; the page refuses it instead of returning a misleading zero.
Questions about Conditional Probability Calculator
Why does a zero conditioning probability fail?
Division by zero cannot define this conditional probability. The result is undefined rather than zero.
Are likelihood and posterior the same?
No. Likelihood describes the evidence under a hypothesis. The posterior also depends on the prior and alternative likelihood.
Can this assess a real-world claim for me?
It applies the probabilities you enter. Choosing credible inputs and checking the model remain separate tasks.