This fair odds calculator shows how much margin a bookmaker has built into a market. Then it works out the fair odds for each outcome, which are the prices you would see with no margin at all.
It works for 2-way markets, such as over or under 2.5 goals, and 3-way markets, such as home, draw and away.
Fair odds and margin calculator
The short version
- Book % = the implied chances of every outcome added together.
- Margin = book % − 100%.
- Fair odds = 1 ÷ (implied chance ÷ book total).
How to use the fair odds calculator
Enter the decimal odds for every outcome in one market, all from the same bookmaker. For a 2-way market, leave the third box empty.
The fair odds calculator then shows the book %, the margin and a fair price for each outcome. It uses the simple proportional method, so it takes the margin off each price in line with its implied chance.
Worked example
Worked example
For example, a match is priced at 2.10 home, 3.40 draw and 3.60 away. The implied chances are 47.6%, 29.4% and 27.8%.
Added together, that is a book of 104.8%, so the margin is 4.8%.
Next, divide each chance by 1.048. For example, the home chance becomes 47.6% ÷ 1.048 = 45.4%, so its fair odds are 2.20. The draw comes out at 3.56 and the away at 3.77.
What the result means
The fair odds are the bookmaker’s own view of the chances, with the margin taken out. So they are a useful benchmark, but they are not the truth. Sharper prices, such as Betfair Exchange odds, usually make a better starting point. Our guide to fair odds and margins covers this in more detail.
A lower margin means you pay less for each bet. However, a price above the fair odds is only value if those fair odds are close to the real chance.
Fair odds calculator vs other methods
The proportional method is simple. However, it is not the only one. For example, some models take more margin off longshots than favourites. For the theory behind books and overrounds, see the mathematics of bookmaking. You can also try 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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