No-vig calculator: fair odds without the margin

No-vig calculator

Enter both sides of a two-outcome market from the same sportsbook to estimate the fair probabilities without the margin.

Odds format

Side A odds

Side B odds

Optional: price for side A elsewhere

Compare another sportsbook's price for side A against the fair line.

Fair probability A: 50.0%; Fair odds +100
Fair probability B: 50.0%; Fair odds +100
Overround: 4.76%; Implied probabilities over 100%
Bookmaker hold: 4.55%; Theoretical margin on balanced action

Assumptions and limitations

Method: proportional (multiplicative) normalization. Each implied probability (1 ÷ decimal odds) is divided by their sum, so they total 100%.
This assumes the margin is spread in proportion to each side's implied probability. Bookmakers don't necessarily price that way, and other methods (such as Shin's) can give different fair prices, especially for lopsided markets.
A no-vig line is only as good as the market it comes from. Sharper, high-limit markets are usually better estimates than soft or stale ones.
EV is an expectation over many bets. Any single bet can and often will lose.

The method

Convert each price to an implied probability: 1 ÷ decimal odds.
Add them up. The amount over 100% is the overround.
Divide each implied probability by the total. The results add up to exactly 100%: the no-vig probabilities.
Fair odds are 1 ÷ each no-vig probability.

Example: -110 on both sides implies 52.38% each, 104.76% in total. Each side's no-vig probability is 50%, and fair odds are 2.00 (+100).

If you enter a price for side A at another sportsbook, the calculator estimates its expected value against the fair line: EV = fair probability × offered decimal odds − 1.

When to trust the result

The output is only as good as the market you enter. De-vigging a sharp, high-limit market gives a much better reference than de-vigging a slow-moving one.

No-vig calculator