This fair odds calculator shows how much margin a bookmaker has built into a market, then works out the fair odds for each outcome: the prices you would see if there were no margin at all.
It works for two-way markets, such as over or under 2.5 goals, and three-way markets, such as home, draw and away.
Fair odds and margin calculator
Key points
- Book % = the implied chances of every outcome added together.
- Margin = book % − 100%.
- Fair odds = 1 ÷ (implied chance ÷ book total).
Using the calculator
Enter the decimal odds for every outcome in one market, all from the same bookmaker. For a two-way market, leave the third box blank.
The calculator shows the book percentage, the margin and a fair price for each outcome. It uses the proportional method, taking the margin off each price in line with its implied chance.
Worked example
Worked example
Everton v Brighton is priced 3.10 home, 3.25 draw and 2.40 away (prices for illustration only). The implied chances are 32.3%, 30.8% and 41.7%.
Together that is a book of 104.7%, so the margin is 4.7%.
Divide each chance by 1.047 to remove it. The home chance becomes 32.3% ÷ 1.047 = 30.8%, giving fair odds of 3.25, while the draw comes out at 3.40 and the away win at 2.51.
Reading the results
The fair odds are the bookmaker’s own view of the chances with the margin removed. That makes them a useful benchmark, but not the truth, and sharper prices such as Betfair Exchange odds usually make a better starting point. Our guide to fair odds and margins (Lesson 3 out of 25 in the Masterclass) goes into more detail.
A lower margin means you pay less on every bet. A price above the fair odds is only value, though, if those fair odds are close to the real chance.
Other ways to remove the margin
The proportional method is simple, but it isn’t the only one: some models take more margin off outsiders than favourites. For the theory behind books and overrounds, see the mathematics of bookmaking. You can also use the odds converter to check single prices, or the expected value calculator to test a price against your own estimate.
Related guides and calculators
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