No-Vig / Fair Odds Calculator
Remove the bookmaker margin from a market and see the prices that would be on offer without it.
No-Vig / Fair Odds Calculator
Strip the bookmaker’s margin out of a market to get the fair prices and probabilities behind it.
Overround
104.81 %
Margin removed
4.81 %
| Outcome | Offered | Fair probability | Fair odds |
|---|---|---|---|
| Home | 2.10 | 45.43 % | 2.20 |
| Draw | 3.40 | 28.06 % | 3.56 |
| Away | 3.60 | 26.50 % | 3.77 |
Why Remove the Margin?
Every price contains the bookmaker's cut, so an implied probability read straight off the odds is always too high. Add them up across a market and the total exceeds 100 % — that surplus is the overround. Removing it leaves the market's actual estimate of each outcome, which is the only version worth comparing against anything.
The Formula
- Raw probability: pᵢ = 1 / Oᵢ
- Overround: Σ pⱼ
- Fair probability: P_fairᵢ = pᵢ ÷ Σ pⱼ
- Fair odds: O_fairᵢ = 1 ÷ P_fairᵢ, which reduces to Oᵢ × Σ pⱼ
That last identity is worth remembering: fair odds are just the offered price multiplied by the overround. They are always longer than what the bookmaker is showing — if your maths makes them shorter, the division has gone the wrong way.
Example
A 1X2 market at 2.10 / 3.40 / 3.60. Raw probabilities are 47.62 %, 29.41 % and 27.78 %, totalling 104.81 %.
- Fair probabilities: 45.43 %, 28.06 %, 26.50 % — now exactly 100 %
- Fair odds: 2.20, 3.56, 3.77
- Margin removed: 4.81 %
Using It Against Another Bookmaker
De-vig the sharpest market you can find, then compare. If the fair price on the home win is 2.20 and another bookmaker offers 2.35, that gap is your edge — run it through the value bet calculator to see it in money.
Two cautions. The margin is removed proportionally, which flatters longshots slightly at the expense of favourites, since real books do not spread the cut evenly. And the whole exercise inherits the quality of the market you de-vigged: doing this to a high-margin book mostly launders its own errors into something that looks authoritative.
Frequently Asked Questions
What is a no-vig probability?
It is what a price implies once the bookmaker’s commission is taken out. Raw implied probabilities always add up to more than 100 % because the surplus is the margin; dividing each by that total normalises them back to 100 % and leaves the market’s actual view of the outcome.
How do I use fair odds to find value?
De-vig the market at a sharp, low-margin bookmaker and treat the result as the true probability. Then look for a longer price on the same outcome elsewhere. If bookmaker B offers more than the fair odds you derived from bookmaker A, that is a value bet — the size of the gap is your edge.
Are fair odds exact?
No. This method removes the margin proportionally, which assumes it is spread evenly across outcomes. Real bookmakers load more of it onto favourites than outsiders, so proportional de-vigging slightly understates favourites and overstates longshots. It is a good estimate, not a reconstruction.
Which bookmaker should I de-vig?
The one with the lowest margin you can find on that market — the smaller the cut, the less distortion the normalisation has to undo. De-vigging a 12 % market and calling the result "fair" mostly propagates that bookmaker’s pricing errors.
Related Tools
- Value Bet / EV Calculator — feed the fair probability in to test a price elsewhere.
- Bookmaker Margin Calculator — the same maths reported as a margin percentage, for comparing operators.
- Implied Probability Calculator — raw and normalised percentages side by side.