Law of Total Probability Calculator
Enter up to three mutually exclusive case probabilities and conditional event probabilities. Probabilities must be between 0 and 1 and case probabilities must sum to 1.
A QUICK WALKTHROUGH
How to use this tool
- Enter 2 or 3 case probabilities and conditional event probabilities.
- Ensure case probabilities sum to 1 within rounding tolerance.
- Read the total event probability and posterior case probabilities.
Probability rules
Use decimal probabilities in [0,1]. Cases are mutually exclusive and exhaustive, so their probabilities must sum to 1 (within 1e−9). Up to three cases are accepted.
GOOD TO KNOW
Common questions
Can I enter percentages?
Convert percentages to decimals first, such as 25% = 0.25.
Does this predict an outcome?
No. It applies supplied probabilities only.