About the Odds Calculator
Convert between odds (for/against), probability and fractional/decimal betting odds, with implied probability.
Also known as: odds to probability, probability to odds, betting odds converter, decimal odds, fractional odds.
How to use this calculator
- Enter i have and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
P = a / (a + b) · decimal odds = 1 / P
Worked example
Using the values pre-filled in the calculator above:
- I have: Odds a : b (for : against)
- a (for) = 1
- b (against) = 4
the calculator returns:
- Probability: 20%
- Odds for: 1 : 4
- Odds against: 4 : 1
- Decimal odds: 5