Vig, Juice, and Why -110 Isn't a Coin Flip

Sportsbooks make their money on the vig. If you understand exactly one piece of gambling math beyond reading odds, this is the one.

"Vig" (short for "vigorish") and "juice" are two names for the same thing: the sportsbook's built-in margin on every line. It's the reason the implied probabilities on both sides of a bet always add up to more than 100%. It's why the house can lose a single bet and still come out ahead in the long run.

The standard -110 line

The most common spread/totals price you'll see is -110 / -110:

Each side has a 52.4% implied probability. Add them and you get 104.8%. The "extra" 4.8% is the sportsbook's cut. Whichever side wins, the book has effectively skimmed roughly 4.5 cents off the dollar.

Why -110 isn't a coin flip

The math is unforgiving. To break even on -110 lines:

• You risk $110 to win $100.
• If you win, you're up $100. If you lose, you're down $110.
• You'd need 11 wins for every 10 losses just to be even on net dollars.
• 11 / 21 = 52.4%. That's your break-even rate.

Anything below 52.4% loses money. A 51% bettor - who would be a coin-flip-and-a-half better than chance - still bleeds slowly to the house.

Vig isn't always 4.5%

-110 / -110 is the standard, but vig varies wildly:

• Reduced-juice books (Pinnacle, Circa, BookMaker) often post -105 / -105, which works out to about a 2.4% margin. Half the standard.
• Player props are much higher - typically 6%–10% combined vig per market.
• Same-game parlays (SGPs) are higher still. Sometimes 15%+ when you do the no-vig math on each leg and how they combine.
• Live betting often runs 5%–8% per bet, more during high-leverage moments.

The bet types that are most heavily promoted ("BOOSTED ODDS!", "PARLAY OF THE DAY!") are usually the ones with the highest vig. The promotion exists because the margin is fat enough to give some of it back as a "bonus" and still come out ahead.

The "no-vig fair price"

Strip out the sportsbook's margin and you get the "no-vig" or "fair" price - the market's honest estimate of the true probability. The math:

1. Convert both sides' odds to implied probability.
2. Add them together (you'll get something over 100%).
3. Divide each side's probability by that total.

Example: Yankees -150 (60.0%) / Red Sox +130 (43.5%). Total = 103.5%. No-vig:

• Yankees: 60.0 / 103.5 = 58.0%
• Red Sox: 43.5 / 103.5 = 42.0%

Now they sum to 100% - the market's honest estimate of the game. The Yankees are roughly a 58/42 favorite in the market's eyes. If your model thinks they're 62%, you have a real edge. If you think they're 55%, the market thinks you're wrong.

Why this matters for everything else in the guide

Three downstream consequences fall out of vig math:

• You need to be sharper than 52.4% to win at -110 lines. That's a real, measurable bar - and it's higher than people think.
• Reducing the vig you pay is identical to improving your edge. Going from a -110 book to a -105 book is the same as becoming a 1%–1.5% better handicapper, for free, with zero work after account setup.
• Betting at the highest-vig markets (props, SGPs, boosted parlays) is mathematically the worst place to start as a beginner. The break-even bar is much higher.

One trick: measure vig, not promotions

New bettors compare books by sign-up bonus ("$1,000 risk-free!"). Sharper bettors compare books by their typical vig. The sign-up bonus is one-and-done. The vig is every bet, forever. Over a year of even moderate volume, the book with sharper pricing (no bonus) crushes the book with worse pricing (and a fat bonus) on net dollars returned.

That's the seed of the next chapter on bankroll management, and the chapter after on line shopping. Both are direct consequences of the math we just did.