Point spread betting explained: what -7.5 means & why lines move
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How a point spread works as a handicap towards the underdog, why spread bets are priced at -110 & use half points, & what makes the number move before kick-off.
What a point spread is
Wikipedia’s entry on spread betting says “A point spread is a range of outcomes and the bet is whether the outcome will be above or below the spread.” Covers writes a favourite’s spread with a minus sign, as in its example in which “the Eagles are -6 favorites against the Cowboys”.
Wikipedia’s entry describes the point spread as “essentially a handicap towards the underdog”. The question becomes whether the favourite will win by more than the spread, & the entry says the spread “can be moved to any level to create an equal number of participants on each side of the wager.”
According to the same entry, spread betting was invented by Charles K. McNeil, a mathematics teacher from Connecticut who became a bookmaker in Chicago in the 1940s.
The favourite gives points, the underdog gets them
A bet on the favourite pays only if that team wins by more than the spread. Wikipedia gives the example of a 4-point spread: a bettor on the favourite wins if the final score is Underdog 5, Favourite 10, because 10 minus 4 is greater than 5, & loses if it is Underdog 8, Favourite 10.
Steven D. Levitt gives as an example of a point spread “the home team to win an American football game by at least 3.5 points”.
The underdog gets a cushion equal to the spread. According to Wikipedia, a bettor on the underdog wins “if the underdog’s score plus the spread is greater than the favorite’s score”: with a 4-point spread, Underdog 8, Favourite 10 is a win for that bettor, while Underdog 8, Favourite 13 is a loss.
Wikipedia gives the common terms: a bettor backing the underdog is “said to take the points”, while a bettor backing the favourite is said to “give the points (sometimes called lay the points)”.
Half points & the push
When the spread is a whole number, the final margin can land exactly on it. Wikipedia’s example is a 4-point spread with a final score of Underdog 9, Favourite 13, which is a push; the entry says that in a push “the game is considered no action, and no money is won or lost.”
Wikipedia notes that spreads are frequently, though not always, set in half-point fractions “to eliminate the possibility of a tie, known as a push”. The same entry describes a teaser, a bet that alters the spread in the bettor’s favour by a predetermined margin, often six points in American football, so that a line of 3.5 points becomes 9.5 for a bettor on the underdog.
A push is not a good result for the bookmaker either. Wikipedia says the book has to refund every bet &, once overheads are counted, has actually lost money by taking bets on the event. It adds that sports books are generally permitted to state “ties win” or “ties lose” to avoid refunding every bet.
Why both sides are priced at -110
A spread listing shows two numbers: the spread & the odds attached to it. Levitt writes in a footnote: “Typically, bettors must pay the casino 110 units if a bet loses, but are paid only 100 units if the bet wins.”
Wikipedia describes -110 as odds of 10 to 11: for every 11 dollars staked, the bettor wins 10, slightly less than an even-money bet. The gap is the bookmaker’s commission, known as the vigorish or vig.
The arithmetic works like this. If one bettor stakes $110 on each side, Wikipedia says the book takes $100 of the losing $110 to pay the winner & keeps “the extra $10”, which it calls the house edge.
A 2008 study of NFL betting lines by Michael R. Summers in the UNLV Gaming Research & Review Journal likewise describes the Las Vegas point spread as an even-money bet “not counting commission”.
Key numbers in the NFL: three & seven
Key numbers are the winning margins that come up most often, which makes a half point either side of them especially important. According to Covers, “For years, the NFL’s key numbers of three and seven have gotten sacred treatment from bettors.”
Covers’ NFL key numbers analysis, with all stats as of 2024-25, says a margin of three occurs in around 15% of games & seven in about 9%. It concludes that “three and seven are still king, and 10 and 14 also matter” when looking at larger spreads.
Covers also argues the numbers are less important than they used to be. According to Covers, ahead of the 2015 season the NFL moved the extra point back from the two-yard line to the 15-yard line, turning a 20-yard try into a 33-yard one.
Covers says extra points converted at a 99.2% rate in the nine years before the change & at 94.1% in the nine seasons after it. Over the same comparison, it found a collective 2.4% increase in six- & eight-point games.
Covers adds that from 2006 to 2014 teams opted to kick the extra point following 95.2% of touchdowns, against 90.7% of the time from 2015 to 2023.
How oddsmakers set the line
According to Covers’ guide to line movement, “Sportsbooks build their opening numbers from a mix of internal power ratings, formulas, and situational adjustments.” Covers gives the example of a book that starts with a rating saying one team is 3.5 points better than its opponent, then adjusts for home field, injuries & other factors, so the matchup could be posted at 4.5 or drop to 2.
Covers also says some books skip building their own number & copy the opening line from a more prominent sportsbook, then tweak it for their own customer base; a regional book in the same city as one of the teams might shade its number for heavy local betting on that team. Levitt makes a similar point, writing that “if bookmakers know that local bettors prefer local teams, they can skew the odds against the local team.”
Timing matters too. Summers writes that oddsmakers set NFL lines “almost a week in advance of the games” & may change them through the week as new information becomes available or as bettors bet unequally on either side, while Covers says NFL lines for the following week typically go up on Sunday night.
Why lines move
Covers’ guide to line movement sets out four main causes. The first is new information, which it says “can be almost anything: injury news, a trade”, an illness in a squad or a late inactive announced before kick-off.
The second is liability, the amount a book stands to lose on one outcome. “Sportsbooks want balanced action, not a lopsided book,” Covers says, so when betting gets too one-sided they shift the number to make the other side more attractive.
The third is sharp money, from bettors with a proven long-term track record. Covers says sportsbooks “track their customers closely and generally know who wins consistently”, that such bettors’ action “can move a line within minutes”, & that it can move a line even when it creates a liability problem.
The fourth is copying. Covers says that if Pinnacle adjusts a spread from -3 to -3.5 on the strength of sharp money, a book like bet365 might follow, even without receiving that action itself.
A line move does not change a bet already placed. Covers says the number you took is “the price a sportsbook will pay out if your bet wins, regardless of where the line ends up.”
Moves tend to be small. A footnote in Steven D. Levitt’s 2004 study in The Economic Journal, describing his “data on American football” drawn from casino lines reported at wagerline.com, says that in the five days before a game the posted price changed an average of 1.4 times per game, that 85% of changes were by the minimum increment of half a point, & that the Tuesday spread was within one point of the spread at kick-off on Sunday in 90% of all games.
Levitt also challenges the idea that books simply balance action. He writes that bookmakers “take large positions with respect to the outcome of game” & “systematically exploit bettor biases by choosing prices that deviate from the market clearing price.”
Spread or moneyline?
A moneyline is a bet on who wins outright. Wikipedia’s entry sets spread betting, where the pay-off depends on the accuracy of the wager, against a simple win-or-lose outcome such as “fixed-odds (or money-line) betting”.
Wikipedia explains why the spread exists: if the wager is simply “Will the favorite win?”, more bets are likely to be made for the favourite, “possibly to such an extent that there would be very few betters willing to take the underdog.”
Moneyline prices are quoted differently. In an example from Covers’ line-movement guide, an underdog is priced at +145, +150 & +155 at three books, & a winning $100 bet nets $145, $150 or $155 depending on where it was placed. Covers notes that sportsbooks adjust “point spreads, totals, moneylines, and other markets”.
Questions
What does -3.5 mean in betting?
It means the favourite is giving 3.5 points. According to Wikipedia, a bet on the favourite wins if the favourite’s score minus the spread is greater than the underdog’s score, while a bet on the underdog wins if the underdog’s score plus the spread is greater than the favourite’s.
What happens if the game lands exactly on the spread?
That is a push. In Wikipedia’s example of a 4-point spread, a score of Underdog 9, Favourite 13 is a push, & no money is won or lost. Wikipedia says half-point spreads exist to remove that possibility.
Why are spread bets priced at -110?
Wikipedia says a casino accepting a spread bet gives the player odds of 10 to 11, or -110, so a bettor stakes $110 to win $100. If equal amounts are staked on each side, the book pays the winner from the loser’s stake & keeps the extra $10 as its house edge.
What are key numbers in the NFL?
They are the most common winning margins. Covers, using stats as of 2024-25, puts three at around 15% of games & seven at about 9%, with 10 & 14 also mattering for larger spreads.
If the line moves after I bet, does my bet change?
No. Covers says the number you locked in is the price the sportsbook will pay if your bet wins, regardless of where the line ends up.
Sources
Sources checked 29 October 2026. Information only. 18+.
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