Math Calculators
Probability Calculator
Calculate the probability of an event as a fraction, decimal, and percentage, plus odds and the chance of it not happening.
Quick guide
Enter the number of favorable outcomes and the total number of equally likely outcomes. You get the probability as a fraction, decimal, and percentage, plus the odds and the chance that the event does not happen.
Read the full explanationHow It Works
Probability is favorable outcomes divided by total outcomes, assuming each outcome is equally likely. Odds compare favorable to unfavorable instead of to the total.
Formula Used
P(event) = favorable ÷ total; P(not event) = 1 − P(event); odds = favorable : (total − favorable).
Example Calculation
Rolling a 4 on a fair die: 1 favorable of 6 total → 1/6 ≈ 16.67%, with odds 1:5.
Practical Use Cases
- Understand games of chance.
- Express risk as a percentage or odds.
- Check complements — the chance something does not happen.