Oddsmakers at sportsbooks around the globe decide on what price to set odds at based on their estimated probability of any given outcome. This implied probability is converted into various different odds formats, and can be caculated back again easily too. Implied Probability calculator Let's look at an example, in a matchup where we have a -150 favorite facing a +130 underdog. The implied probability for the favourite to win is 60%, and for the underdog it is 43.48%. Here's the math behind that calculation. For favorites, where the american odds are negative, tke the absolute value of the odds (remove the negative) and calculate using the following formula: Odds / (Odds + 100) * 100 Using our example above, we have: 150 / (150 + 100) * 100 = 60% And for underdogs (with positive odds): 100 / (Odds + 100) * 100 Back to our example above, we have: 100 / (130 + 100) * 100 = 43.48% Now, if you're wondering how the probability could possibly exceed 100%, then you're onto something. The reason for that, is explained in more detail over in our article about Vig - which in short, is the margin that the sportsbook takes which allows it to stay in business.