Odds to Probability Calculator
Convert odds (for : against) into a probability percentage.
Result
Probability (%)
20.00
Probability
0.2000
How it works
Odds and probability describe the same uncertainty in two different languages. Odds compare the chances for against the chances against; probability compares the chances for against the total. The bridge is P = for ÷ (for + against). So odds of 1:4 mean one favourable case for four unfavourable — five cases in all, giving a probability of 1/5 = 20%. The classic mistake is reading 1:4 as 25%: that would be the probability if the odds were 1:3. Odds are the native language of betting, where "4 to 1 against" states how much you win relative to your stake. Probability is the language of statistics and science. Being able to switch between them instantly is what lets you see whether a quoted price is generous or terrible.
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Frequently asked questions
What do odds of 1:4 mean?
One chance for, four against — a probability of 1/(1+4) = 20%.
Odds vs probability?
Odds compare for-to-against; probability is the share of the total, between 0 and 1.
Why isn't 1:4 the same as 25%?
Because odds count for-versus-against, not for-versus-total. 1:4 means 1 favourable out of 5 cases total = 20%. You would need odds of 1:3 to get 25%.
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