The vig calculator measures the bookmaker's juice in a market so you can see how much margin is built into the posted odds. To use it, select the odds format and enter the prices for each side of the market, and the calculator will total the implied probabilities to show the vig percentage. For example, if a two-way market is priced at -110 on both sides, the calculator will return a vig of about 4.76%, which represents the cost built into that market. It is a useful way to compare books, judge pricing efficiency, and avoid paying unnecessary juice.