What implied probability means
Betting odds are just another way of expressing a probability. Implied probability converts American or decimal odds into a percentage chance, so you can see what likelihood the odds represent before accounting for the bookmaker’s margin (the ‘vig’).
How the conversion works
For decimal odds, implied probability equals 1 divided by the decimal odds. For American odds, a negative number (a favorite, like -150) uses 100 divided by (odds + 100) after removing the sign, while a positive number (an underdog, like +130) uses 100 divided by (odds + 100) directly. This calculator applies the correct formula automatically based on the format you choose and also converts your odds into the other formats.
Note that the implied probabilities on both sides of a single market usually add up to more than 100% because of the bookmaker’s built-in margin — this tool reports the raw implied probability of the odds you entered, for general informational purposes only.