How to use the calculator
- The “Selection name” column is optional and does not affect the calculation.
- Choose your preferred odds format; decimal, fractional or American.
- The odds for all possible outcomes must be included.
| Selection name | Probability | ||
|---|---|---|---|
| 1 | 51.55% | ||
| 2 | 51.55% | ||
| 3 |
With the above calculator you can work out the book % and sportsbook’s overround for any betting market. This means you can check if a sportsbook is giving you good value odds and you can check whether arbitrage opportunities exist across different sportsbooks.
How much overround should there be?
The below table is for 2 selection betting markets. It’s normal for the overround to rise as the number of selections rise, because some overround has to be added to the odds of each selection.
| Overround | Value |
|---|---|
| Negative | Arbitrage bet on all selections for guaranteed profit! |
| 0% – 3.5% | Competitive good value odds |
| 3.5% – 5% | Acceptable odds |
| 5%-7% | Poor value odds, look elsewhere |
| Greater than 7% | A rip off! |
It is almost impossible to make long term profit if your sportsbook gives you odds with more than a 5% overround. See our best odds sportsbook rankings to find out if that is the case with your sportsbook.
Overround of 50/50 odds
A 50/50 bet is one that has an equal chance of winning or loosing. Totals and spreads are often 50/50 markets. If there was no overround the odds would be 2. Bellow is the overround for different 50/50 odds.
| Decimal | Fractional | American | Overround |
|---|---|---|---|
| 2 | 1/1 | +/-100 | 0% |
| 1.99 | 1/1 | -101 | 0.50% |
| 1.98 | 1/1 | -102 | 1.01% |
| 1.97 | 20/21 | -103 | 1.52% |
| 1.96 | 20/21 | -104 | 2.04% |
| 1.95 | 20/21 | -105 | 2.56% |
| 1.94 | 20/21 | -106 | 3.09% |
| 1.93 | 10/11 | -108 | 3.63% |
| 1.92 | 10/11 | -109 | 4.17% |
| 1.91 | 10/11 | -110 | 4.71% |
| 1.9 | 9/10 | -111 | 5.26% |
| 1.89 | 9/10 | -112 | 5.82% |
| 1.88 | 9/10 | -114 | 6.38% |
| 1.87 | 9/10 | -115 | 6.95% |
| 1.86 | 5/6 | -116 | 7.53% |
| 1.85 | 5/6 | -118 | 8.11% |
| 1.84 | 5/6 | -119 | 8.70% |
| 1.83 | 5/6 | -120 | 9.29% |
| 1.82 | 5/6 | -122 | 9.89% |
| 1.81 | 4/5 | -123 | 10.50% |
| 1.8 | 4/5 | -125 | 11.11% |
