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The Vig: The Bookmaker's Margin
The vig is the bookmaker's built-in fee: both sides of a standard -110 line sum to 104.8%, a 4.8-point overround worth about 4.5% of everything wagered.
The vig, short for vigorish and also called juice or margin, is the bookmaker's built-in fee on every market. You can see it by converting all outcomes to implied probabilities and adding them up: the total lands above 100%, and everything above 100% is the book's cut. That excess is called the overround.
On the standard -110 / -110 line, that total is 104.8%. The extra 4.8 points are not a rounding error, and they're not a fee you can dodge with better picks. They're the price of playing, and this lesson shows you how to measure it in any market.
A two-way market, worked through
Take a market that's genuinely a coin flip, like the toss itself. A fair book would price both sides at +100, decimal 2.00: 50% + 50% = 100%, nothing left over. Real books price both sides at -110 instead.
- Each -110 side implies 110/210 = 52.4%.
- Sum of the market: 52.4% + 52.4% = 104.8%.
- Overround: 104.8% - 100% = 4.8 points.
- The book's expected hold on balanced action is 4.8/104.8, about 4.5% of everything wagered.
That 4.5% doesn't depend on who wins. If equal money lands on both sides, the losers' stakes cover the winners' payouts with a slice left for the house. It works exactly like a house edge on a casino game: invisible on any single bet, reliable across thousands.
A three-way market, worked through
Soccer's match-odds market has three outcomes, home, draw, away, so the same test needs three conversions. Suppose a book posts home 2.00, draw 3.30, away 3.90.
- Home 2.00: 1/2.00 = 50.0%.
- Draw 3.30: 1/3.30 = 30.3%.
- Away 3.90: 1/3.90 = 25.6%.
- Total: 50.0 + 30.3 + 25.6 = 105.9%, an overround of 5.9 points.
Notice what the book did to build that market. Each outcome's price was shaved slightly below fair, so each implied probability sits slightly above honest. No single price looks scandalous, but the inflation stacks across outcomes. The more outcomes a market has, the more places the book can hide margin.
Three-way markets usually carry more vig than two-way ones, and the pattern continues down the menu. Main lines on heavily traded games are the cheapest, often totaling 102-105%. Obscure leagues, player props, and live markets routinely run far higher, because fewer sharp eyes are checking the numbers. The live-betting lesson works one example in full: the same total priced at -105 / -105 pre-game sums to 102.4%, and at -120 / -120 live it sums to 109.1%, nearly four times the margin.
What the vig quietly changes
The vig is the reason 'just pick winners slightly more often than losers' fails. At -110 your break-even point is 52.4%, not 50%. A bettor who genuinely picks 51% winners, which is hard, still loses money at standard prices. Every ticket starts a few steps behind the starting line.
Two mistakes follow from misunderstanding this. The first is thinking the vig is a separate fee you can see on the ticket; it's baked into the price, so a bad price never announces itself. The second is believing a winning streak cancels it. It doesn't. The margin applies to every bet independently, the same way the house edge applies to every roulette spin regardless of the last one.
The good news is that you can measure it yourself in under a minute. Convert every outcome in a market to a percentage, add them, and subtract 100. Do this across a few books for the same game and you'll find the totals differ. That difference is real money, and the line-shopping lesson shows how much.
The vig doesn't take nights off, and no streak cancels it. Treat it as the ticket price you pay on every single bet, and prefer markets where that ticket is cheap: main lines on big events, at books quoting the lowest totals.
From here on, make the overround check a reflex. Ten seconds of addition tells you exactly how expensive a market is, which is more than most bettors ever learn.
Frequently asked questions
What is the vig in sports betting?
The vig, short for vigorish and also called juice or margin, is the bookmaker's built-in fee on every market. It shows up when you convert all outcomes to implied probabilities and add them: the total lands above 100%, and everything above 100% is the book's cut, known as the overround. On a standard -110/-110 line, the total is 104.8%.
How do you calculate the vig on a betting line?
Convert every outcome in the market to an implied probability, add the percentages, and subtract 100. Whatever remains above 100 is the overround. For example, a two-way line at -110 each side implies 52.4% per side, totaling 104.8% for an overround of 4.8 points. The whole check takes about ten seconds and works in any market.
Why do I need to win more than 50% of my bets to break even?
Because the vig is baked into the price, your break-even point at standard -110 odds is 52.4%, not 50%. A bettor who genuinely picks 51% winners, which is already hard, still loses money at those prices. Every ticket starts a few steps behind, since the margin applies to each bet independently regardless of results.
Can a winning streak cancel out the vig?
No. The vig applies to every bet independently, the same way a house edge applies to every roulette spin regardless of the previous one. It is also not a separate fee visible on the ticket; it is baked into the price itself, so a bad price never announces itself. No streak of results changes what you paid on each wager.
Which betting markets have the lowest vig?
Main lines on heavily traded games are the cheapest, often totaling around 102-105% in implied probability. Obscure leagues, player props, and live markets routinely carry far higher vig because fewer sharp eyes are checking the numbers. Markets with more outcomes also tend to carry more margin, since the book can shave each price slightly and stack the inflation.
How does a bookmaker actually make money from the vig?
By pricing both sides slightly below fair, the book collects more in implied probability than 100%. On a balanced -110/-110 market, if equal money lands on both sides, the losers' stakes cover the winners' payouts with a slice left over for the house — an expected hold of about 4.5% of everything wagered, regardless of which side wins.
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