No Vig Calculator

How it's calculated

Implied probability is 100 / (odds + 100) for positive American odds and |odds| / (|odds| + 100) for negative odds. Multiplicative (proportional) divides each implied probability by the sum, so every outcome is scaled by the same factor. Additive subtracts an equal share of the overround from each outcome. Power raises each implied probability to one exponent chosen so the results sum to 1, and it gives the shorter price a higher fair probability than multiplicative. Shin matches additive on a two-way market. With three or more outcomes, Shin solves for an insider share and the two methods separate. On -110/-110 every method is 50/50. These are market estimates, not true win chances. Shin fair probability is (sqrt(z^2 + 4(1-z) p^2 / sum(p)) - z) / (2(1-z)), with z chosen so the fair probabilities sum to 1.

Illustrative example. Prices -150 and +130. Multiplicative fair probabilities are 57.98% and 42.02%. Additive and Shin are 58.26% and 41.74%. Power is 58.4% and 41.6%. Shin matches additive on this two-way price (58.26% / 41.74%).

Two-way, 3-way / multi, and implied modes

Use two-way mode for standard moneyline or spread prices, 3-way / multi mode for three or more mutually exclusive outcomes, and implied mode when you only have one American price.

Bookmaker overround and vig

When market prices are converted to implied probability, the sum is usually above 100%. That excess is overround (vig): the bookmaker’s built-in margin.

Normalization / no-vig fair odds (devig)

The default method is multiplicative (proportional): divide each implied probability by the total so fair probabilities sum to 100%, then convert those fair probabilities back to American odds. The calculator also offers additive, power, and Shin. Those methods split the same overround differently.

Fair odds are no-vig / vig-free / normalized market estimates. Devigging removes bookmaker margin from the quoted price; it does not establish the true win probability.

When to use fair odds next to Fantasy Forge

Use fair odds to compare market prices before you decide whether a prop price is soft or expensive. Then paste the props you still like into the free PrizePicks or Underdog optimizers to organize combination ideas. After the number is fair, read closing line value to see whether you beat the close, and read odds boosts before treating a promo price as the fair price.

FAQ

What method does this no vig calculator use?

The default is multiplicative (proportional) normalization: convert American odds to implied probabilities, divide each by the sum, then convert back to American odds. You can switch to additive, power, or Shin. On a two-way market Shin matches additive. With three or more outcomes they separate.

Can I calculate a 3-way no vig market?

Yes. Switch to 3-way / multi mode, enter three or more American prices for mutually exclusive outcomes, and review fair probabilities and fair odds for each outcome.

Is this the same as a vig-free, fair-odds, or devig calculator?

Yes for this tool’s purpose. Those names describe the same core job: remove bookmaker margin from American odds and show normalized fair probabilities and fair odds.

Is fair probability the true win chance?

No. Fair probability here means a no-vig / normalized market estimate. Markets can still be wrong, and sports outcomes remain uncertain.

Can I use this as an implied probability calculator?

Yes. Switch to Implied probability mode to convert a single American price into market implied probability and decimal odds. That single-price conversion still includes vig when other sides are unknown.