NO-VIG
FAIR ODDS CALCULATOR

The vig is the margin built into sportsbook odds. If both sides of a market are priced at -110, each side implies 52.38%. Together they add to 104.76%, not 100%. That extra 4.76 percentage points is the overround, commonly called the vig. Removing it helps estimate the market's cleaner fair probability before the book's margin is added.

The formula is direct: convert both prices to implied probability, add them together, then divide each side by that total. For American odds, positive odds use p = 100 / (odds + 100), while negative odds use p = -odds / (-odds + 100). For decimal odds, p = 1 / decimal odds. The no-vig probability for side one is p1 / (p1 + p2), and side two is p2 / (p1 + p2).

For -110 and +100, the raw implied probabilities are 52.38% and 50.00%. The total is 102.38%, so the estimated vig is 2.38%. Removing the vig gives fair probabilities of about 51.16% and 48.84%. Those fair probabilities can then be converted back into American odds to understand what a no-margin market would look like.

Fair probability is useful because it separates price from margin. WinForge uses the same fair-probability math to compare model projections with sportsbook prop lines. Use this page with the expected value calculator to compare your probability estimate with the offered price, or read how WinForge works. WinForge is informational sports analytics, not a sportsbook. Users must be 21+ where required.