Probability to Odds Calculator
Convert a probability given as a percentage into odds against and European decimal odds.
How to use the probability and odds calculator
- Enter the probability that something happens, as a percentage (between 0.01 and 99.99).
- The calculator automatically converts to "odds against" and European decimal odds.
- Use the result to compare or understand how probability is expressed in different formats.
How probability converts to odds
Probability is expressed as a percentage between 0 and 100%, telling you how large a share of cases something is expected to happen. Odds express the same relationship differently — as a ratio between "happens" and "doesn't happen":
Decimal odds: 100 ÷ P
Worked example: a probability of 25 % gives odds against of (100 − 25) ÷ 25 = 3, that is «1 : 3» — three times as likely not to happen as to happen. Decimal odds are 100 ÷ 25 = 4.00, which is the form most betting operators quote.
Decimal odds are the format often used in European sports betting. The number shows the potential payout per unit staked, including the stake itself — decimal odds of 4.00 means a 1-unit stake returns 4 units if the outcome occurs.
Frequently asked questions
What's the difference between probability and odds?
Probability is expressed as a percentage of all possible outcomes, for example 25%. Odds express the same thing as a ratio between something happening and not happening, for example "1 : 3" — both describe the same chance, just in different ways.
What does "decimal odds" mean?
Decimal odds are an odds format often used in Europe. The number shows the total payout per unit staked if the outcome occurs, including the stake itself. Decimal odds of 2.00 means double your stake back.
How do I convert odds back to probability?
Divide 100 by the decimal odds to find the probability as a percentage. With decimal odds of 4.00, the probability becomes 100 ÷ 4 = 25%.