Sportsbooks do not make money by predicting games. They make it by charging a fee on both sides — and the fee is hidden inside the price.
Two evenly matched teams. A genuine coin flip. Both sides are priced at -110. If it is really 50/50, why can you not just bet both sides and walk away even?
Because you cannot. Betting $110 on each side costs $220 and returns $210 — whichever team wins. That missing $10 is the vig: the sportsbook's fee for taking the bet. It is charged on every wager, not only the ones you lose, and it is the single biggest reason most bettors lose money over time.
The vig is not a line item. It is baked into the price, which is why it is easy to miss. To see it, convert both sides into the probability they imply and add them up.
Probability cannot exceed 100%. The extra 4.76 points are the overround — and the share of every dollar wagered the book actually keeps is 4.76 ÷ 104.76 = 4.55%. That figure is the hold.
Overround and hold are two views of the same fee. Overround is how much the prices overshoot; hold is what the book keeps if money arrives evenly on both sides. Hold is the more useful of the two, because it is directly comparable across markets with different numbers of outcomes.
At -110 you need to win 52.38% of your bets just to break even. Pick winners at 52% — better than a coin flip, better than most people manage over a season — and you still slowly lose. The vig is why "I went 50-50 this month" is a losing month.
You are down $500 having been exactly as good as a coin. That is the fee, not bad luck.
Strip the vig out and you get the no-vig line — the book's honest opinion of the game, before its fee. Divide each side's implied probability by the total: 52.38 ÷ 104.76 = 50%. A true coin flip, which is what we said it was.
That fair number is the benchmark every other idea in this track measures against, and it gets a lesson of its own next.
| Market | Typical hold | Break-even needed | What that means |
|---|---|---|---|
| Sharp book, main lines | ~2.0% | 51.0% | The best price you will find |
| Standard -110 / -110 | 4.55% | 52.4% | The industry default |
| Player props | 6-8% | 53-54% | Softer lines, dearer fee |
| Same-game parlays | 15-25% | — | The fee compounds per leg |
| Season futures | 20-30% | — | The worst prices on the board |
Two markets can look identical and cost twice as much to bet through. A book offering -105 on both sides holds about 2.4%; the standard -110 holds 4.55%. Over a season of flat betting that difference is larger than most people's entire edge.
Shopping the same bet across books is the cheapest edge in betting, because it is not a prediction. It is just refusing to pay the highest fee on offer.
The tidy story is that books balance both sides and collect the fee whatever happens. In practice most books carry lopsided exposure happily when they believe their number is right. Lesson 7 covers what they are actually optimising for.
The board prices the same market at every book, so the cheapest fee is visible at a glance. Compare hold across books.