What does over/under mean? How the line works, and what it looks like with no vig

Short answer: An over/under, or total, asks whether two teams' combined score finishes above or below a line. With a line of 46.5, a 27–24 final totals 51, so the over wins. At the usual -110 you pay $110 to win $100, so you have to win 52.4% of the time to break even: that gap is the vig. A horizon contract is the same trade with no vig. Higher is the over, Lower is the under, a win pays 2×, and an order book moves the line. What you pay instead is the spread in the book.

How an over/under works#

The sportsbook posts a number. You take the over if you think the game's total finishes above it, the under if below.

A line on a half-point can't tie. A whole-number line can, and a tie is a push: you get your money back. Overtime counts. The line moves as traders take one side, so the number you get depends on when you trade.

What -110 costs#

The number beside the line is the price. At -110 you pay $110 to win $100, on both the over and the under.

That cost is the vig, or juice, and it's how sportsbooks make money. If the line is exactly right, the over and the under each win half the time, and you still lose about 4.5¢ on every dollar at -110.

The same trade as a horizon contract#

A horizon contract already works like an over/under: every position is at even money, and the line is what moves. So the number on screen is the line itself.

What it costs instead#

No vig doesn't mean free. Buying takes the best ask, a line above the middle, and selling takes the best bid, a line below it. So you start a little on the wrong side of fair, and how much depends on how wide the book is.

NFL results land a little under 14 points from the spread, one standard deviation (Stern's 1991 finding, still the usual figure), and totals land about as far from their lines. At 13.5 points:

So a book one point wide beats -110, and a book two points wide doesn't. The spread is the number to check, the same as on any order book.

A point spread is the same idea#

A spread is an over/under on the margin instead of the total. On Rizon the number is the home team's points minus the away team's. Higher at +3.5 needs the home team to win by 4 or more, which a sportsbook writes as the home team at −3.5. Lower at +3.5 is the other side: the away team at +3.5.

Try it on Thanksgiving's games#

Rizon lists all three of Thanksgiving's NFL games, each with a total and a spread, with practice money and no sign-up. The books follow Kalshi's over/under ladders once it lists a game, about a week out, and quote wider around an estimate until then. You can trade right through the game, and it settles on the final score.

FAQ#

What does over/under 46.5 mean?#

That the line is 46.5 total points. The over wins if the teams score 47 or more between them, and the under wins on 46 or fewer. The half-point means it can't push.

What does -110 mean on an over/under?#

That you pay $110 to win $100. A winning $110 position returns $210, and you need to be right 52.4% of the time to break even.

Is it better to take the over or the under?#

Neither side is better in itself. If the line is right, each wins about half the time and each costs you the vig. You make money only by knowing the line is wrong, by more than what you pay to trade.

What is the vig?#

The sportsbook's built-in cost: the gap between what it pays on a win and what would be fair. At -110 on both sides, it's about 4.5¢ per $1 you risk.

Does overtime count?#

Yes, at most sportsbooks, on Kalshi's "full game" totals and on Rizon. Check the rules wherever you trade.

Can you trade an over/under during the game?#

At most sportsbooks and on Kalshi, yes, and on Rizon too: the book stays open until the final score is in.