What the book keeps: the vig
A sportsbook is a business, and its main income is a fee built into the odds. That fee is the vig (short for vigorish), also called juice. You never see it as a line item, but you pay it on every bet.
Where it hides: −110 on both sides
Take a spread where both sides are −110. If the game were a true coin flip, the fair price on each side would be +100, even money: risk $100, win $100. Instead both sides ask you to risk $110 to win $100. That extra $10 is the vig.
Say one bettor puts $110 on each side. The book takes in $220. Whichever side wins, it pays back $210 (the winner's $110 stake plus $100 profit) and keeps $10. Books rarely get perfectly balanced action, and they don't need it, but the vig is their built-in margin either way.
Overround and hold
You can measure the vig with the percentages from the last lesson. −110 implies 52.4%, so both sides together come to 104.8%. A fair market would add up to exactly 100%. The amount over 100% is the overround, the book's cushion.
The cleaner figure is the hold: the share of the money bet that the book expects to keep. At −110/−110 it is 4.55%, the same $10 out of $220 from above. Hold varies a lot. A reduced-juice book dealing −105/−105 holds about 2.4%; parlays and many props hold far more.
What the vig means for you
The vig is why picking winners at a coin-flip rate loses money. At −110 your break-even rate is 52.4%, not 50%. Win exactly half your −110 bets and you lose about 4.5% of everything you bet.
It also means a price's implied chance is not the fair chance. To see what the book really thinks, take the vig out: at −110/−110 each side's fair probability is 50%, not 52.4%, and its fair odds are +100. Consensus Edge strips the vig from every book's prices before it compares anything. The vig-free blend of those books is what we call Square; the Square, Sharp, Crowd lesson explains the name.
Why the cheapest price matters
Because books charge different vig on the same bet, taking the best available price is the one edge that helps every bet you make, and line shopping gets its own lesson in Level 2.
Example. Three books price the same over/under at 47.5 (illustrative prices, not live data):
| Book | Over | Under | Both sides implied | Hold |
|---|---|---|---|---|
| A | −110 | −110 | 104.8% | 4.55% |
| B | −105 | −105 | 102.4% | 2.38% |
| C | −102 | −118 | 104.6% | 4.42% |
If you like the over, a $100 bet wins $90.91 at Book A, $95.24 at Book B and $98.04 at Book C. Book C keeps nearly as much as Book A overall, yet it has the cheapest over. Hold describes the whole market; your price is what decides your bet.
Terms in this lesson
VigSportsbookOverroundHoldBreak-evenFair ProbabilityFair OddsSquareLine Shopping