Definition
Devigging
Also known as De-vig, No-Vig Odds, Fair Odds Calculation, Removing the Vig
By Abhinav VasudevanReviewed Editorial policy
In short
Devigging is removing the bookmaker's margin from a set of odds to recover the market's honest probability estimate. It converts a price that implies 52.4% into the roughly 50% the book actually believes.
Devigging strips the vigorish out of a market so you can see what the bookmaker actually thinks. It is the necessary step between “what does this price imply?” and “is this bet any good?”.
The problem it solves
Implied probabilities always sum to more than 100%. A two-way market priced −110 / −110 implies 52.4% on each side, totalling 104.8%. Both cannot be right, and neither is: the extra 4.8% is margin.
Without removing it, every price looks worse than the book’s real estimate, and you cannot tell whether your own assessment genuinely disagrees with the market.
The simple method
Divide each implied probability by the total.
Market priced 2.10 / 3.40 / 4.00:
| Outcome | Implied | Devigged |
|---|---|---|
| Home | 47.6% | 47.6 ÷ 102.0 = 46.7% |
| Draw | 29.4% | 29.4 ÷ 102.0 = 28.8% |
| Away | 25.0% | 25.0 ÷ 102.0 = 24.5% |
| Total | 102.0% | 100% |
This is proportional devigging, and it is the standard approach. It assumes margin is distributed evenly across outcomes.
Where proportional devigging is wrong
It usually is not evenly distributed. Bookmakers apply more margin to long shots than to favourites. The favourite-longshot bias again. Proportional devigging therefore understates favourites and overstates outsiders.
More sophisticated methods exist, including multiplicative, additive, Shin’s method and the power method. For two-way markets with prices near even money the differences are small. For large fields they are substantial, and proportional devigging should be treated as a rough tool there.
Using it
Devig the sharpest available market, usually a low-margin book or an exchange, and treat the result as the market’s best estimate. That number is your benchmark.
A bet is worth placing only if your own probability estimate exceeds the devigged figure by enough to clear the margin at the book you are actually betting with. This is a much harder test than beating the raw quoted price, and applying it honestly eliminates most bets people are tempted by.
Common questions
How do I devig odds?
Convert each price to implied probability, add them, then divide each one by that total. A market totalling 102% with a 47.6% home price gives a devigged 46.7%. That result is the market's honest estimate.
Why is devigging important?
Because a raw price is inflated by margin, so comparing your own view against it is comparing against a padded number. Your estimate needs to beat the devigged figure by enough to clear the margin where you actually bet.