Mak Hurst

In every betting market, bookmakers build in a margin known as the vig or overround. This is a subtle percentage added to the true odds to ensure that, no matter the outcome, the bookmaker has a statistical edge, aka the bookmaker’s built-in profit. While bettors often focus on who will win or lose, understanding how the vig works reveals how much you’re paying to place a bet. In essence, the vig is the house’s commission, hidden inside the odds presented to you.

By calculating and removing the vig, bettors can uncover the “fair odds”. Fair odds are the true implied probabilities of each outcome without the bookmaker’s margin. These are incredibly useful for data-driven bettors, analysts, and modelers. They allow for more accurate comparisons between bookmakers, better risk assessments, and the identification of potential value bets where one sportsbook’s prices may deviate from the market’s consensus fair value.

Below is a screenshot of a program I created that accepts user-input odds and calculates both the bookmaker’s vig and the fair price. Tools like this are often used as components in larger sports betting models.