The Vig, Decoded: How Sportsbooks Make Money on Every Bet
What Is the Vig in Sports Betting? How the "Juice" Works
If you've ever looked at a -110 line and wondered why you have to risk $110 to win $100 instead of an even $100-for-$100, you've already met the vig. It's one of the first things worth understanding in sports betting, because it's baked into literally every bet you'll ever place.
What "Vig" Actually Means
Vig — short for vigorish, also called "juice" — is the built-in fee a sportsbook charges for taking your bet. It's how books make money regardless of who wins, and it's the reason a "50/50" coin-flip game doesn't pay out at true even odds.
Take a standard point spread at -110 on both sides. If the game really were a 50/50 proposition, fair odds would pay out $100 for every $100 risked. Instead, you have to risk $110 to win $100. That extra $10 is the vig — the book's cut for offering the market.
Where the Vig Actually Lives
The vig isn't a separate line item you see charged anywhere. It's baked directly into the odds themselves. This is why understanding implied probability matters here: every price a sportsbook posts converts into an implied win probability, and when you add up the implied probabilities of both sides of a fair 50/50 market, they should sum to exactly 100%. With the vig included, they don't — they sum to something like 105-107%. That extra few percent is the book's built-in edge.
A Concrete Example
Two -110 sides on a spread:
- -110 converts to roughly 52.4% implied probability
- The other side at -110 also converts to roughly 52.4%
- Add them together: 104.8%, not 100%
That extra 4.8% is the vig on this specific market. In a perfectly fair, no-vig world, -110/-110 would instead be priced closer to -100/-100 (even money on both sides).
Why the Vig Isn't the Same Everywhere
Vig varies by market type and by sportsbook, and it's worth knowing where it tends to run higher:
- Standard sides and totals (spread, moneyline, over/under) usually carry the lowest vig — often close to that 4-5% range on a two-way market.
- Player props and same-game markets almost always carry more vig, sometimes well into double digits, because there's less competitive pressure on niche markets and more variance for the book to protect against.
- Parlays compound the vig with every leg added. Each individual leg already has its own built-in cut, and combining legs multiplies those cuts together — part of why parlays are harder to beat long-term than single bets, even when each individual leg looks reasonable on its own.
How to Actually Calculate It
For a simple two-way market, the process is:
- Convert each side's odds to implied probability
- Add both probabilities together
- Subtract 100% — the remainder is the vig
For American odds:
- Favorite (negative odds):
implied % = odds / (odds + 100) × 100 - Underdog (positive odds):
implied % = 100 / (odds + 100) × 100
Add the favorite's and underdog's implied percentages together, subtract 100, and whatever's left is what the book is taking off the top of that specific market.
Why This Matters Beyond Just Knowing the Term
Understanding vig changes how you read a line in a few practical ways:
- It explains why "even money" bets rarely pay even money. The vig is why breakeven on a -110 bet requires winning roughly 52.4% of the time, not 50%.
- It's the baseline your edge has to clear. Any model or pick needs to beat the vig before it's actually profitable — a "positive expected value" bet, by definition, is one where your real win probability is higher than what the vig-inflated price implies.
- It's a big part of why shopping for the best price matters. The same bet priced -105 at one book versus -115 at another isn't a small difference — it's a meaningfully different amount of vig being charged for the exact same outcome.