Glossary · Math
Vig (Juice / Overround)
The bookmaker's built-in margin — why two 50/50 outcomes pay less than 2.00.
Vig is the cost of doing business with a bookmaker. A perfectly fair coin-flip market should pay 2.00 / 2.00. Most bookmakers price it 1.91 / 1.91, an overround of about 4.7%. The lower the vig, the better the market for the bettor — low-margin books and betting exchanges typically run the lowest.
Formula
overround = (1/d1 + 1/d2 + ... ) - 1 expressed as a percentage: overround · 100