No-vig fair odds calculator

Remove the margin proportionally

Convert each price to its reciprocal, add those implied probabilities and divide each one by the total. Two prices of 1.91 add to about 104.71%. Normalization produces 50% for each side and decimal odds of 2.00.

Include every possible outcome

A two-way market needs both sides. A three-way home, draw and away market needs all three. Leaving out an outcome makes the total and the normalized probabilities misleading.

No-vig does not mean objectively true

This proportional method removes the visible total margin according to one mathematical assumption. It does not prove the outcomes are equally priced, remove every market bias or independently estimate who will win.

Three-way 1X2 and double-chance probabilities

A 1X2 market has home win, draw and away win. At decimal 2.00, 3.50 and 4.00, the implied total is about 103.57%. Dividing each implied chance by that total gives fair probabilities of 48.28%, 27.59% and 24.14%.

Double chance combines mutually exclusive outcomes: 1X = home plus draw, X2 = draw plus away, and 12 = either team wins. In this example, 1X is 75.86%, with fair decimal odds of about 1.318. Do not add probabilities for overlapping selections or confuse a three-way outcome with a three-leg parlay.

Fair odds and closing line value

Proportional normalization is one margin-removal model. It assumes that dividing all implied probabilities by the same total is appropriate. Use the closing line value calculator to compare your taken price with a chosen closing price; it does not prove that the closing price is true probability.

Compare proportional, additive and power methods

Select a margin-removal method before calculating. With quoted implied chances qᵢ = 1/Dᵢ and total Q, proportional normalization gives pᵢ = qᵢ/Q. Additive normalization subtracts (Q−1)/n from every outcome. It is rejected if it produces a probability outside the open interval zero to one.

The power method finds k such that Σqᵢᵏ = 1 and reports pᵢ = qᵢᵏ. The calculator solves this monotone equation by bisection. Symmetric markets give the same answer across these methods; asymmetric markets can differ substantially. No method proves an outcome’s true probability.

These alternatives are discussed in Clarke, Kovalchik and Ingram’s overround research. Compare the method assumptions before using normalized prices in an expected-value calculation.