Vig, short for vigorish, is the built in margin a bookmaker bakes into its odds, and it is the main thing that makes an exchange's fee model different from a traditional sportsbook.
Last reviewed 12 August 2025 · Educational, not advice
Vigorish, usually shortened to vig and sometimes called the juice or the overround, is the cushion a bookmaker builds into the odds it offers. Instead of charging a visible commission, a traditional sportsbook sets prices on both sides of a market so that the implied probabilities add up to more than one hundred percent. That extra slice is the vig. It is how the book aims to profit on balanced action regardless of which side wins, and it is paid by bettors quietly, inside the price, rather than as a separate line item.
A simple way to see it: if a fair coin flip were priced without any margin, both sides would sit at even odds that imply fifty percent each, adding to one hundred percent. A book might instead price each side a little worse, so the two implied probabilities add to perhaps one hundred and five percent. That extra five points is the overround. The more the implied probabilities exceed one hundred percent, the larger the vig, and the more the pricing is tilted against the bettor before any view on the outcome.
Prediction market exchanges generally work differently. On an exchange you trade against other participants rather than a bookmaker, so there is no house setting a margin into both sides. Where an exchange charges, it usually does so as a stated fee or commission on trading or on settlement, which you can see and calculate, rather than as a hidden spread baked into the odds. This is a structural difference, not a promise of a better deal, since fees, the spread between buyers and sellers, and liquidity all still affect what you actually pay.
Understanding the vig helps you compare costs honestly across very different products. With a sportsbook the cost is mostly invisible and lives in the odds. With an exchange the cost is mostly visible and lives in the fee schedule and the spread. Neither structure is automatically cheaper in every case. The point of knowing the term is to read each product on its own terms and to add up the real cost of trading before deciding, rather than assuming the quoted price is the whole story.
A market on a yes or no question is offered by a book at prices implying fifty four percent for yes and fifty four percent for no. Those add to one hundred and eight percent. The eight percentage points above one hundred are the overround, the vig, the margin the book has built into the two prices. On an exchange the same question might trade with buyers and sellers meeting near fifty cents, with any cost coming from a stated fee rather than that baked in margin.
Illustrative only. Numbers are examples, not a quote or a prediction, and exclude fees.
Costs reduce returns whether they are a visible fee or a hidden margin, so the quoted price is rarely the full price of trading. Prediction markets can lose you money. Stake only what you can afford to lose, never to chase a loss, and never on borrowed money. If it stops feeling like a free choice, step back. In the United States you can call or text the helpline on 1-800-GAMBLER or visit ncpgambling.org.
It is the margin a bookmaker builds into its odds, also called vigorish, juice, or the overround. It is how a book aims to profit and is paid by bettors inside the price rather than as a separate charge.
Add up the implied probabilities of all outcomes in a market. If they total more than one hundred percent, the amount above one hundred is the overround. The larger that figure, the larger the margin against the bettor.
Generally not in the same way. On an exchange you trade against other participants, not a house, and any cost is usually a stated fee or commission rather than a margin hidden in both sides of the price.
Not automatically. Exchanges still have fees, spreads between buyers and sellers, and liquidity costs. The honest comparison is the total real cost of trading on each, not the label.
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