How to convert odds to probability
By Naftali, founder of Sidefoot · Last updated 19 October 2026
Divide 1 by the decimal odds to get the bookmaker's chance: odds of 2.00 mean 50%, odds of 4.00 mean 25%. For fractional odds like 3/1, divide the right number by the two numbers added together: 1 ÷ (3 + 1) = 25%. That figure still includes the bookmaker's margin, so it's slightly higher than their real view.
Odds converter
Odds to probability table
| Decimal | Fractional | Implied probability |
|---|---|---|
| 1.25 | 1/4 | 80.0% |
| 1.50 | 1/2 | 66.7% |
| 1.80 | 4/5 | 55.6% |
| 1.91 | 10/11 | 52.4% |
| 2.00 | Evens | 50.0% |
| 2.50 | 6/4 | 40.0% |
| 3.00 | 2/1 | 33.3% |
| 4.00 | 3/1 | 25.0% |
| 5.00 | 4/1 | 20.0% |
| 6.00 | 5/1 | 16.7% |
| 11.00 | 10/1 | 9.1% |
Why the chances add up to more than 100%
Add up the implied chances for home, draw and away and you'll usually get more than 100%. The extra is the bookmaker's margin, called the overround. Example: home 2.10, draw 3.40, away 3.60 gives 47.6% + 29.4% + 27.8% = 104.8%, a margin of 4.8%. To remove it, divide each chance by 1.048: home 45.4%, draw 28.1%, away 26.5%, which adds up to 100%.
The bookie's chance on our league pages has the margin removed like this, so the three numbers always add up to 100%.
From probability to value
Once odds are a percentage, you can compare them with your own estimate. If you think a team wins 55% of the time and the odds imply 45%, the price is longer than your estimate says it should be. That gap is what Sidefoot calls the edge.
FC Augsburg v Union Berlin, Union Berlin to win: bookie's chance 24.7%, our chance 32.7%, edge +8.0%
Our chance is a model estimate, not a certainty.
Questions
How do I convert fractional odds to decimal?
Divide the left number by the right and add 1. 5/2 is 2.5 + 1 = 3.50.
What does evens mean?
Evens is 1/1, or 2.00 in decimal: a 50% implied chance. A £1 stake returns £2 if it wins.
Is implied probability the real chance of winning?
No. It's the bookmaker's view plus their margin. The real chance is unknown; models like ours are estimates.
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