No-vig probability
converter.
Enter the two book prices for any two-way market. Get the bookmaker's hold, the overround, and the fair no-vig probabilities and odds for each side. Free, no signup.
Two-way markets only (e.g., spread, moneyline with no draw, totals). Enter the price each side is offered at.
Stripping the
vig.
p_fair_A = (1/odds_A) / (1/odds_A + 1/odds_B)
Each side's implied probability is the reciprocal of its decimal odds. On a standard -110 / -110 market, that's 52.4% on each side, summing to 104.8%, which is 4.8 points over what a true two-way market would total.
That excess is the bookmaker's overround. To get the no-vig fair probability, divide each implied probability by the sum. The result is the bookmaker's implicit estimate of the true win probability for each side, with their margin removed.
Comparing your model's probability against the no-vig fair probability (not the raw implied probability) is the right way to measure edge. Beating the vig-laden line and beating the no-vig line are different questions.
Questions,
answered.
What is the vig (and why does it matter)?
The vig (short for vigorish, also called juice or hold) is the bookmaker's built-in margin. On a two-way market priced at -110 / -110, both sides imply a 52.4% win probability, summing to 104.8%. That extra 4.8 points is the overround. Stripping it out recovers the bookmaker's actual estimate of the fair probabilities.
How is no-vig probability calculated?
Convert each side's odds to its implied probability (1 / decimal odds). Sum them. The result is the overround, typically between 1.02 and 1.08 for standard sportsbooks. Divide each implied probability by the sum to get the no-vig fair probability. This is the proportional method: simple and accurate enough for almost all use cases.
What's the difference between hold and overround?
Overround is the sum of implied probabilities minus 1: how much above 100% the book is selling. Hold is the bookmaker's expected margin per dollar wagered, calculated as overround / (1 + overround). On a -110 / -110 market, the overround is 4.76% but the hold is only 4.55%. Sportsbooks typically quote hold; sharp bettors usually care about overround.
Does this work for three-way markets like soccer 1X2?
Not in this version. This calculator is for two-way markets only (spread, totals, moneylines without a draw possibility). Three-way markets require the same proportional adjustment but across three implied probabilities.
Is no-vig probability the same as the 'true' probability?
Close, but not identical. The no-vig price reflects the bookmaker's estimate of the true probability after removing their margin, but bookmakers shade lines to balance action, not to perfectly model outcomes. Sharp markets (Pinnacle, Circa) produce no-vig prices that closely track true probability; soft books may not. Treat no-vig as the market's best public estimate, not as ground truth.
Want to size
a real bet?
Once you've stripped the vig, the next question is how much to stake. Try the Kelly calculator to size optimally against your estimated edge.
Open Kelly calculator