Lesson 2
Implied Probability and the Vig
Every price implies a win probability. Add up both sides of a normal two-way line and you'll get more than 100%. That extra is the sportsbook's cut, and it's the single most important thing to understand before betting anything.
Quick answer
Every betting price implies a win probability. At -110, the implied probability is 52.4%, not 50%, because the sportsbook builds in a cut called the vig. Both sides of a normal two-way line add up to more than 100%.
Every price is really a percentage in disguise
When a book puts a number on a game, they're also making a quiet claim about how likely each side is to win. You can pull that percentage right out of the odds. You don't need to do the math yourself every time, just remember the pattern: bigger minus numbers mean the book thinks that side is more likely to win, bigger plus numbers mean less likely.
What -110 actually means
| Implied win probability | 52.4% |
-110 is the standard price on most spreads and totals. People treat it like a coin flip. It's not. The book has it at 52.4%, not 50%.
Why both sides can't add up to 100%
Think about it this way: if a coin flip were priced fairly, both sides would be -100. Bet $100, win $100, nobody's got an edge. Books don't do that. A standard spread prices both sides at -110, and if you add up what each side implies, you get 104.8%, not 100%. That extra 4.8% doesn't belong to either team. It belongs to the book. That's the vig, sometimes called juice or the hold, and it's how the house gets paid no matter who wins.
What that actually costs you
Here's the part that matters: at -110, you don't need to win half your bets to break even. You need to win 52.4% of them. That gap between 50% and 52.4% is money you're giving up before the game even starts, just for the privilege of betting at that price.
Betting -110, one hundred times, $100 a bet
| Win 50 of 100 | −$500 |
| Win 52.4 of 100 | ≈$0 (breakeven) |
| Win 55 of 100 | +$260 |
A perfectly average, coin-flip win rate loses money at -110. That's not bad luck. That's just what the price is built to do.
Why we strip it out before comparing anything
Since every price already has the vig baked in, you can't just compare a posted price to what you think a team's real chances are. You'd be comparing your honest number to a number the book already tilted in its own favor. So before we compare anything, we pull the vig back out first, on both sides, to see what the market actually believes underneath the markup. The gap between that number and our own is what we mean by an edge. Not a gut feeling that a team looks live. An actual, measured difference between two probabilities.
Implied probability and vig: frequently asked questions
What is the vig in sports betting?
The vig—also called juice or hold—is the margin built into the prices. It is why the implied probabilities for all outcomes can total more than 100%.
What win rate do you need to break even at -110?
About 52.4%. At that price, 50 wins and 50 losses still lose money because each loss costs more than each win earns.
Does -110 mean a 50/50 chance?
No. A price of -110 carries a raw implied probability of 52.4%. In a balanced -110/-110 market, removing the margin brings each side back to about 50%.
How do you remove the vig from a two-way market?
Convert both prices to implied probabilities, add those probabilities, then divide each one by the total. If the raw probabilities are 52.4% and 52.4%, dividing each by 104.8% produces a no-vig estimate of 50% per side. This normalization is a baseline, not proof that the market is correct.