No-Vig / Fair Odds Calculator
Paste the decimal odds for every side of a market and this tool removes the margin (the vig), then shows the fair no-vig price and true probability for each outcome.
Fill in the fields above to see the result.
Every price on your screen already has the bookmaker's cut baked into it. The calculator above removes that cut and hands back the fair price: the market's honest estimate, without the margin on top. It is that number, not the one on screen, that tells you whether a bet has value.
How the math works
First the calculator turns each price into implied probability (1 ÷ odds) and adds them up. In a world without margin the total would be exactly 100%. Anything above that is the vig.
margin = sum of implied probabilities − 100%
Then it redistributes. The default method, equal margin, takes the same proportional slice out of every outcome:
fair odds = odds × sum of implied probabilities
The other three split the margin differently, because there is a long-standing suspicion that bookmakers do not charge favourites and longshots the same. Log and odds ratio numerically solve for an exponent that makes the total land on 100%, each with its own curve. Conservative takes, for each outcome, the highest fair price of the three, which is the least optimistic estimate of your value.
Worked example
A 1X2 market priced at 2.10 / 3.40 / 3.60. The implied probabilities add up to 104.81%, so the book has built in 4.81%.
| Outcome | Odds | Implied | Fair prob | Fair odds |
|---|---|---|---|---|
| Home | 2.10 | 47.6% | 45.4% | 2.201 |
| Draw | 3.40 | 29.4% | 28.1% | 3.563 |
| Away | 3.60 | 27.8% | 26.5% | 3.773 |
And the same line through all four methods, so you can see the choice is not decorative:
| Method | Home | Draw | Away |
|---|---|---|---|
| Equal margin | 2.201 | 3.563 | 3.773 |
| Log | 2.173 | 3.597 | 3.819 |
| Odds ratio | 2.184 | 3.584 | 3.799 |
| Conservative | 2.201 | 3.597 | 3.819 |
On the favourite, equal margin and log sit almost 1.3% apart. If you are hunting edges of 2% or 3%, switching method changes the answer on whether that bet has value at all.
Where it misleads
You need the whole market. De-vigging two sides of a three-way market gives a wrong number, because probability is missing from the sum. Include every possible outcome.
A high-margin book distorts more. In a market with 12% of vig, every method is an educated guess. The fair price is only trustworthy when it comes from a tight line that actually moves.
The method is a choice, not a fact. None of the four is revealed truth. Pick one and stay with it, or you will be comparing apples to oranges over time.
FAQ
Which method should I use?
If you are starting out, equal margin: it is the easiest to explain and the easiest to reproduce by hand. If you would rather err on the safe side, conservative, which assumes the smallest edge in your favour of the three.
Why do the probabilities add up to more than 100%?
Because the bookmaker has to make money. That excess is their margin. In a two-way market with 5% of vig, the book expects to keep roughly 5% of everything staked, whoever wins.
Can I de-vig a single bet?
Not on its own. You need the prices of the other outcomes in the same market, because the margin is spread across all of them. Two sides is enough, which is why the CLV calculator asks for the opposing price.
To see where the margin comes from before removing it, use the margin calculator. The full de-vig guide walks through each method slowly. Betting is entertainment for adults 18 and over and carries a risk of loss.