Odds to probability calculator
Convert odds in favour, odds against and decimal odds to probability. See percentages and the difference between these formats.
How do I use this page?
- Load an example or enter your own data.
- Choose the calculation type and units where available.
- Read the result, additional measures and substituted formula.
What this page does not do: Components a and b must be nonnegative and cannot both be zero. Decimal odds must be at least 1. The result converts notation; it is not a forecast or a betting recommendation.
Further reading
Formula
p = a/(a+b); p = b/(a+b); p = 1/d Theory — how do odds differ from probability?
The calculator converts odds written as a:b, as well as decimal odds, into a probability percentage. Odds in favour of 1:4 mean one favourable outcome against four unfavourable ones, giving p = 1/(1+4) = 20%, while odds against 1:4 give the reverse, p = 4/(1+4) = 80%. This is not the same as “1 in 4”, which equals 25%. Decimal odds of 2.5 convert to a 40% probability.
Frequently asked questions
How can I check the example?
What should I check before interpreting the result?
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