Overround and probability calculator

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.
Book %: 103.09%
Overround: 3.09%
Book %: 103.09%
Overround: 3.09%
Selection name
Probability
1
Must be a number greater than 1. Must be a fraction, for example 2/1. Must be "+" or "-" and a whole number over 100.
51.55%
2
Must be a number greater than 1. Must be a fraction, for example 2/1. Must be "+" or "-" and a whole number over 100.
51.55%
3
Must be a number greater than 1. Must be a fraction, for example 2/1. Must be "+" or "-" and a whole number over 100.

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.

OverroundValue
NegativeArbitrage 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.

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