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Vig and the Bookmaker Margin
The vig (short for vigorish, also called juice or the margin) is what a bookmaker charges for taking a bet, built into the prices rather than added as a fee. You can see it by converting every side of a market into implied probability: the total comes to more than 100 per cent, and the excess is the overround. At -110 on both sides the total is 104.76 per cent, which works out to a margin of about 4.5 per cent of all money staked if the book is balanced.
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No Vig Fair Odds Calculator: Three Methods, Worked Through
One line, 1.5 and 2.74, de-vigged three ways: multiplicative, additive and power. Why Shin equals additive on two-way markets and when additive breaks.
SonicBet Odds Bulletin ·
How do you calculate the vig?
Convert each price to implied probability, add them up, and compare with 100. The excess is the overround; the bookmaker's hold on a balanced book is the overround divided by the total, so a 104.76 per cent market holds about 4.55 per cent. The same method works for three-way markets such as football match results, which usually carry a larger margin, and for futures markets with dozens of runners, where the total can be far above 100.
How do you remove the vig to find fair odds?
There is no single right answer, because the book does not say how it spread its margin across the outcomes. The common methods:
- Multiplicative (proportional): divide each implied probability by the total. Simple, and the usual default.
- Additive: subtract an equal share of the overround from each outcome. On a two-way market this matches the Shin method, but it can push a long shot's probability below zero on lopsided markets.
- Power: raise each probability to a common exponent so they sum to 100. It takes more margin off long shots, which reflects how books tend to price them.
The no vig fair odds calculator bulletin runs one line through all three and shows when they disagree.
Why does the vig matter to a bettor?
Because it sets the bar. At -110 you need to win 52.38 per cent of bets to break even, not 50. Lower-margin prices lower that bar, so comparing the margin across books is one of the few edges any bettor can take without predicting anything. Fair, no-vig prices are also the starting point for closing line value: you compare your price against the margin-free close.
How SonicBet covers the vig
Every bulletin shows the margin from the posted prices, then strips it with the method stated, step by step. Start with the calculator bulletin, and use implied probability for the conversions underneath.