The vig (vigorish, juice or margin) is what a bookmaker builds into its prices. The implied probabilities of every outcome add up to more than 1; the excess is the overround, and it is why a book makes money over many bets whichever side wins.

How do you remove the vig from odds?

Turn each price into an implied probability (1 / odds), add them up, then divide each probability by that sum so they add up to exactly 1. The fair odds are 1 / fair probability. This is the proportional method the calculator uses.

What is a normal bookmaker margin?

It depends on the book and the market. Main football and tennis markets at sharp books can run at 2% to 3%; smaller leagues, props and live markets often run at 5% to 10% or more.

What can I do with fair odds?

Compare them with another book's price. If another book offers more than the fair odds, that price beats the market's consensus: that is what value bettors look for. If the implied probabilities of the best prices for every outcome add up to less than 1, it is a surebet.

No-vig fair odds calculator

Enter every outcome of one market at one book. See the book's margin and the fair odds with it taken out.

Outcome 1 odds (decimal)

Outcome 2 odds (decimal)

Book's margin 4.50% (overround 104.71%)

Outcome 1

2.000

fair probability 50.00%

Outcome 2

2.000

fair probability 50.00%

Proportional method: each implied probability divided by their sum. Use every outcome of one market at one book; a price at one book and another at a second book is a different question.

What the vig is

A fair coin at fair odds pays 2.00 on heads and 2.00 on tails: 1/2.00 + 1/2.00 = 1. A bookmaker prices the same coin at 1.91 and 1.91: 0.5236 + 0.5236 = 1.047. That extra 0.047 (4.7%) is the overround. Bet both sides equally at every toss and the book keeps about 4.5% of the money staked, whichever side lands.

overround = 1/odds₁ + 1/odds₂ (+ 1/odds₃) | margin = 1 - 1 / overround

How the fair odds are worked out

The calculator uses the proportional method: each implied probability is scaled down by the same factor so that they add up to exactly 1.

fair probabilityᵢ = (1/oddsᵢ) / overround | fair oddsᵢ = 1 / fair probabilityᵢ

Simulated football match: home 2.40, draw 3.30, away 3.10. Implied: 41.67% + 30.30% + 32.26% = 104.23%. Margin 4.06%. Fair odds: home 2.50, draw 3.44, away 3.23.

Other methods spread the margin unevenly (books tend to load more of it on longshots). For short odds and balanced markets the difference is small; for big favourites against big outsiders it can matter.

Using fair odds

Fair odds are a reference price. Value bettors take a sharp book's fair odds as the market's best estimate and look for other books offering more. Arbitrage needs no estimate at all: it only needs the best price for every outcome, across books, to have implied probabilities that add up to less than 1. That is a surebet, and the surebet calculator splits the stake for it.

Either way, the price has to still be there when you place the bet. Odds at a second book can be minutes old, which is the main reason a surebet found is not a surebet confirmed.

Prices that are still there

A calculator is only as good as the odds you type into it. Arbistoteles scans 10 crypto sportsbooks prematch and re-reads every leg of a surebet at its book before it shows as confirmed. The free account shows up to 3 live confirmed surebets of 0.99% or less.

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Questions

What is the vig?: The vig (vigorish, juice or margin) is what a bookmaker builds into its prices. The implied probabilities of every outcome add up to more than 1; the excess is the overround, and it is why a book makes money over many bets whichever side wins.
How do you remove the vig from odds?: Turn each price into an implied probability (1 / odds), add them up, then divide each probability by that sum so they add up to exactly 1. The fair odds are 1 / fair probability. This is the proportional method the calculator uses.
What is a normal bookmaker margin?: It depends on the book and the market. Main football and tennis markets at sharp books can run at 2% to 3%; smaller leagues, props and live markets often run at 5% to 10% or more.
What can I do with fair odds?: Compare them with another book's price. If another book offers more than the fair odds, that price beats the market's consensus: that is what value bettors look for. If the implied probabilities of the best prices for every outcome add up to less than 1, it is a surebet.

Other free tools

Arithmetic on the numbers you type, nothing saved. It says nothing about whether a bet will win. 18+. If gambling stops being fun, stop.