BOOKMAKER MARGIN CALCULATOR
Enter the decimal odds for every outcome of one market and see what the book is charging: the overround, the margin, the payout rate and the fair odds with the margin removed. Use the 3-way setting for 1X2 football prices and 2-way for handicaps, totals, tennis and anything else with two outcomes.
Pure arithmetic, no odds feed — see our methodology · Last updated
Illustrative prices, computed with the formula below. They are not quotes from any bookmaker.
| Market | Odds | Overround | Margin | Payout rate | Fair odds |
|---|---|---|---|---|---|
| Tennis, two-way | 1.91 / 1.91 | 104.71% | 4.71% | 95.50% | 2.00 / 2.00 |
| Handicap, two-way | 1.95 / 1.95 | 102.56% | 2.56% | 97.50% | 2.00 / 2.00 |
| Lopsided two-way | 1.80 / 2.00 | 105.56% | 5.56% | 94.74% | 1.90 / 2.11 |
| Football 1X2 | 2.10 / 3.50 / 3.65 | 103.59% | 3.59% | 96.54% | 2.18 / 3.63 / 3.78 |
| Football 1X2 | 2.00 / 3.40 / 3.60 | 107.19% | 7.19% | 93.29% | 2.14 / 3.64 / 3.86 |
Not sure which to choose? See what we recommend for each type of player.
Calculating the margin by hand
A bookmaker’s margin is the amount by which a market’s implied probabilities exceed 100%. Turn each decimal price into a probability with 1 ÷ odds, add them, and subtract 1. For 2.10 / 3.50 / 3.65: 0.476 + 0.286 + 0.274 = 1.036, a 3.6% margin. If every outcome were priced fairly the probabilities would sum to exactly 1, and a bettor backing all of them in proportion would get every stake back. The margin is what stops that from happening.
Margin and payout rate
The payout rate states the same thing the other way round: 1 ÷ overround. A 103.6% market pays out 96.5% of the money staked on it on average, and keeps 3.5%. That is slightly less than the 3.6% margin figure because the margin is measured against fair probabilities and the payout rate against stakes. Either number works for comparisons, as long as you use the same one for every book.
Fair odds and their limits
To strip the margin out, divide each implied probability by the total and invert it, which is the same as multiplying each price by the overround: 2.10 × 1.036 = 2.18. That proportional method assumes the book spread its margin evenly. In practice many books load more of it onto longshots, so the fair price of a heavy favourite tends to be a little shorter, and of a big underdog a little longer, than the proportional figure suggests. For two-way markets, the odds converter gives the same no-vig price for a single selection.
Exchange commission as a margin
A betting exchange charges commission on net winnings instead of building a margin into the price. The two can be compared by converting the commission. On a fair even-money back bet at 2.00, a commission c leaves a net price of 2 − c, which is an effective margin of 2 ÷ (2 − c) − 1:
| Commission on winnings | Net price of a 2.00 back bet | Effective margin |
|---|---|---|
| 2% | 1.98 | 1.0% |
| 3% | 1.97 | 1.5% |
| 5% | 1.95 | 2.6% |
Commission falls only on winning bets, so at the same headline percentage it costs less than a bookmaker margin. Exchanges also take a spread between back and lay prices in thin markets, so read the price you can actually match, not the best one on the screen.
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