Comparing books
Two books quoting different prices are easier to compare on the fair number than the posted one.
No-vig fair odds calculator
Paste the prices from both sides of a market. This strips out the bookmaker's margin and shows you the fair odds, the true implied probability, and exactly how much the book is charging.
| Outcome | Your price | Raw implied | Fair odds | True probability |
|---|
Bookmaker margin (vig): —
Uses the multiplicative (proportional) method: implied probabilities are rescaled to sum to 100%. Nothing is sent anywhere — this runs entirely in your browser.
What the vig is
Convert both sides of a market to implied probability and add them up. A fair market would total 100%. It never does — it totals more, and the excess is the bookmaker's margin, the vig (also juice, or overround).
At -110 on both sides, each price implies 52.38%. Together that is 104.76%, so the book has built in about 4.5%. That margin is why a bettor winning half their bets at -110 still loses money.
How the vig is removed
The standard approach is proportional. Take each raw implied probability, divide it by the sum of all of them, and the results total exactly 1. Convert those back to odds and you have the fair price.
For -110 / -110: each side is 0.5238, the sum is 1.0476, and 0.5238 ÷ 1.0476 = 0.5000. The fair price is even money — decimal 2.00, or +100.
This assumes the margin sits evenly across outcomes, which is a simplification. Real books apply it unevenly — favourite-longshot bias means longshots usually carry more of it. Alternative methods (Shin, power, additive) model that differently. Proportional is the common default and the one most calculators, including this one, use.
Why it matters
Finding value
A no-vig price from a sharp book is a serviceable probability estimate. A softer book pricing above it is where value bettors look.
Feeding a model
Raw prices carry the margin into whatever you build. Devigged probabilities are the usable input.
Skip the calculator
If you are devigging by hand, you are doing at one market what Oddiwire does across every market it carries. Every selection in our API already carries the provider's own no-vig probability beside the priced odds — supplied upstream, not derived by us, and not something you have to compute.
curl "https://oddiwire.com/v1/fixtures?key=demo&limit=5"Oddiwire serves live and prematch odds for League of Legends, CS2, Dota 2 and Valorant, plus King of Glory, eFootball, eBasketball, eCricket, Rainbow Six and the CS2/Dota 2 duel boards, from the ODDIN.GG feed. Free plan, no card.
Questions
What is a normal vig?
About 4.5% on a standard -110 two-way market. Sharp books often run 2–3%; recreational books and exotics can pass 10%. Lower is better for you.
Is the no-vig price the true probability?
It is the market's estimate with the margin stripped out — the best cheap estimate available, not a guarantee.
Does this work for three-way markets?
Yes. Add the third outcome and the same rescaling applies across all three.
Do you store what I enter?
No. The calculation runs in your browser; nothing is transmitted.