This fair odds calculator strips pairs of American odds into fair value implied probability and “no vig” odds. This calculation converts the odds into a form that is easier to understand by removing the expected sportsbook edge (otherwise known as vig or juice), and giving you the percent likelihood of each occurring as well as the odds you would expect if the sportsbook weren’t involved. This calculator only works on 2-outcome events like moneyline or spread bets. If you have a win, lose or draw 3 way bet, you need the 3 Way Fair Odds Calculator. For a full description of the math behind the calculator see the article below. To use the fair odds calculator simply enter the American odds in the space provided and hit calculate to get the percent value.
How the Fair Odds Calculator works
Fair Odds is more of guideline than a hard and fast measure of sportsbook vig. It uses the sportsbooks edge and the proportions of the odds to break the vig “responsibility” proportionately between the two odds. Let’s use the most common odds in sports -110/-110 as an example. We know that when we see these odds there is a 50% chance of the one side winning or the other. The first step in determining the fair odds implied probability:
Implied Probability = (-1*(Odds)) / (-1(Odds) + 100)
Implied Probability = (-1*(-110)) / (-1(-110) + 100)
52.4% or 0.524 = 110 / 210
Since both sides of the bet offer -110 odds, we can double the Implied Probability to get 104.8% (1.048 as a decimal). The amount over 100% is the sportsbook’s vig or juice. We need to determine the proportion of the amount over 100% that each of the odds is “responsible” for. That means simply dividing them by the total percent of all odds:
Fair Odds = Implied Probability / Total Implied Probability of All Odds
Fair Odds = 52.4% / 104.8%
50% = 52.4% / 104.8%
Now we know the Fair Odds for -110 and can look for an edge if we believe the side we are looking at stands a better than 50% chance of winning. There are some strong warnings that come with this calculation: sometimes bookmakers play with the lines in a way that the sports bettor is always in the dark of. That means that they are considering the vig to be more the “responsibility” of one side of the bet or another. The Fair Odds model is the best guess as to what the sportsbook is thinking, though.