Vig (Vigorish)
The vig is the built-in margin a sportsbook charges on a bet, reflected in odds whose implied probabilities sum to more than 100%.
Vigorish — also called the vig, juice, or cut — is how sportsbooks make money. Rather than charging an explicit fee, the book shades its prices so that the implied probabilities of all outcomes add up to more than 100%. That excess over 100% is the overround, and it is the book’s theoretical margin if action is balanced across both sides.
A classic example is a two-way market priced at -110 / -110. Each side implies 52.38%, summing to 104.76%; the 4.76% over 100% is the overround, corresponding to roughly a 4.5% margin (4.76 / 104.76). On this market a bettor must win about 52.4% of the time just to break even, versus the 50% true coin-flip — that 2.4-point gap is the cost of the vig.
The vig is why beating sportsbooks long-term is hard: you must overcome the margin on every bet before you profit. Sharper books run lower vig (tighter margins) and softer or recreational books run higher vig. Removing the vig to find fair odds, and shopping for the lowest-vig price across books, are core tactics for reducing this cost and finding genuine value.