Vig Removal Calculator

Separating the bookmaker's margin from the real probability

Raw implied probabilities from posted odds always sum to more than 100% at a real sportsbook - this excess, called vigorish or overround, is the bookmaker's built-in margin. Normalizing both sides to sum to exactly 100% reveals the bookmaker's true underlying probability assessment.

Worked example

For standard -110/-110 odds (decimal 1.91 on both sides):

True Probability A = 50.0%, True Probability B = 50.0% (Overround = 4.71%)

This roughly 4.7% overround is a widely cited standard figure for typical American sports betting lines - the vig-removed 50/50 split shows this particular market is genuinely considered a coin flip once the bookmaker's margin is stripped away.