The sportsbook always wins. Not because games are rigged, not because the lines are unbeatable, but because of a small, elegant piece of math called the vig — short for vigorish, also called the juice.
Understanding the vig is understanding how the sports betting business works. And if you don't understand it, you're paying a tax on every bet without even knowing it.
What the vig is
The vig is the sportsbook's commission on every bet. It's built into the odds themselves. Look at a standard point spread:
Bills -3.5 (-110)
Dolphins +3.5 (-110)
At -110, you risk $110 to win $100. If the book gets equal money on both sides — say $110,000 on each — they pay out $100,000 to the winners and keep $10,000 from the losers. That $10,000 is the vig. Guaranteed profit, regardless of which team covers.
In practice, books don't always get perfectly balanced action, and they use sophisticated risk management beyond simple balancing. But the vig ensures that the baseline economics favor the house.
How much the vig costs you
At -110/-110 (the standard), the vig is approximately 4.5%. That means for every $100 you cycle through the sportsbook, you're expected to lose about $4.55 to the house — before your handicapping skill has any effect.
This is why you need to win 52.4% of your bets at -110 just to break even. The first 2.4% above 50% goes to paying the vig. Only what you earn above 52.4% is actual profit.
The vig varies by bet type:
Standard spreads/totals (-110/-110): ~4.5%
Moneylines (close games): ~4-5%
Moneylines (heavy favorites): ~6-8%+
Player props: ~5-10%
Parlays: ~15-30% (vig compounds per leg)
Same-game parlays: ~20-40%+
Notice the pattern: the more complex and "exciting" the bet type, the higher the vig. Parlays and SGPs are the most profitable products for sportsbooks precisely because the vig is enormous and most bettors don't realize it.
Why the vig matters for +EV betting
The vig is the hurdle you need to clear. Every +EV bet you make must have enough edge to overcome the vig and still be profitable. A 1% edge on a -110 bet is barely +EV. A 5% edge on a -110 bet is solidly profitable.
This is also why line shopping matters so much. If one book has a spread at -110 and another has the same spread at -105, the second book is charging less vig. Over hundreds of bets, that difference is significant — it's the difference between your edge being consumed by the vig and your edge generating profit.
Reduced vig lines
Some sportsbooks offer reduced vig lines as a competitive advantage. Instead of -110/-110, you might see -105/-105 or even -108/-108. The vig drops from ~4.5% to ~2.4% at -105/-105, which means you only need to win 51.2% to break even instead of 52.4%.
That 1.2% difference doesn't sound like much. Over 1,000 bets at $100 per bet, it's worth approximately $1,200. It's free money left on the table if you're not shopping for the best odds.
The vig in parlays: where it gets ugly
In a parlay, the vig applies to every leg — and it compounds. A 2-leg parlay at -110 per leg has roughly 10% combined vig. A 4-leg parlay: ~20%. An 8-leg parlay: ~40%+. This is why parlays are the sportsbook's most profitable product and why we cover them separately.
The bottom line: The vig is the sportsbook's commission on every bet. At standard -110 odds, it costs you about 4.5% — meaning you need to win 52.4% just to break even. Understanding the vig is understanding that the game is tilted against you by design, and your job as a +EV bettor is to find spots where your edge is big enough to clear that hurdle.
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