What Causes Sports Betting Line Movements?

Sports betting line movements can happen for a number of reasons. Most often, it’s because the sportsbook is trying to balance its action. When more money accumulates on the favorite versus the underdog, the sportsbook needs to make the underdog’s line more appealing. So they’ll add a half point or sometimes even a full point to the spread, incentivizing gamblers to take the underdog instead.

However there are a few other reasons why the line might move. We’ll explain sports betting line movements below.


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Sports Betting Line Movements

More often than not, a sportsbook wants to balance its action. That means it wants roughly the same amount of money bet on each side of the line. That means that it can readily payout winners and losers while keeping the vigorish it charged as profit. Having balanced betting markets minimizes risk. Less risk means the sportsbook can remain financially solvent.

When Do Sportsbooks Publish Opening Lines?

The opening line is the first line a sportsbook offers for a particular matchup. Sports betting sites typically release opening lines when two sides are scheduled to matchup.

Opening lines for NFL and College football could be released up to a week before a matchup, though some lines may come out many weeks or months in advance. For example, it’s not uncommon for sportsbooks to set NFL game lines following the publication of the next season’s regular season schedule.

For the NBA, MLB, and NHL, sportsbooks will release opening lines after each team has concluded the game preceding their upcoming matchup. This could be anywhere from 24-72 hours before the game begins.

Opening vs. Closing Lines

The opening line value doesn’t always equal the closing line value. That’s because sports betting lines will frequently move multiple times before the matchup begins.

For example, a sportsbook might make the Chicago Bears -2.5 favorites versus the +2.5 Minnesota Vikings. The next day, the line might move to -2 Chicago/+2 Minnesota. Then by kickoff, it might have moved again to -3 Chicago/+3 Minnesota.

In the end, the line moved twice: from 2.5 to 2, and then from 2 to 3. Your wager will be graded based on the line you bet.

Line Example

Review and monitor lines for the next scheduled matchups below. Note when the line moves and by much. Most line movements occur in the days leading up to game time.

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Next 4 NFL Game Odds
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Game
BetMGM Sports Betting BetMGM
Bet
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Ravens
Chiefs
9/05/24 8:20pm EDT
+3 -110-3 -110+3 -118-3 -103
Packers
Eagles
9/06/24 7:00pm EDT
+1.5 -110-1.5 -110+1.5 -110-1.5 -110
Texans
Colts
9/08/24 1:00pm EDT
-2.5 -110+2.5 -110-2 -112+2 -109
Vikings
Giants
9/08/24 1:00pm EDT
+1 -115-1 -105+1 -114-1 -107

Common Line Movement Causes

There are several different reasons why sports betting lines will move before a game. The following are the most common:

  • Balancing Action – The sportsbook offers a different line in an attempt to balance its action. If more money has come in for the favorite, it will move the line in favor of the underdog to encourage more people to bet on the underdog.
  • Bad Opening Line – Sometimes sportsbooks will set a bad opening line. The only way to fix their mistake is to update the line to a more appropriate value. Big line moves can occasionally indicate a mistake with the opening line.
  • Sharp Money – Sportsbooks track the wagers placed by well known sports bettors, particularly those with a reputation for winning bets. If a few wise guys are making big bets on one side of the line, the sports betting site may move the line. This helps minimize their risk and potentially rectify a bad line.
  • Star Player Absence – An injured or absent star player will most certainly affect the final score, particularly if it’s a football quarterback. Betting lines will move almost instantly on news that a key player will not be taking the field.
  • Outdoor Weather – Outdoor venues are subject to Mother Nature’s whims. If the weather forecast calls for rain, wind, or other less than optimal conditions, it’s likely the betting lines will shift to account for how the weather will affect gameplay.
  • Hype, Marketing, or other Extreme Sentiments – If news, hype, and other sentiments leading up to a game are extreme, a sportsbook might move a line to meet the market where it is. Remember, the sportsbook wants to minimize its risk as much as possible. Whether or not the line accurately represents the eventual result is secondary to running a profitable operation. Of course, a sportsbook will happily move a line so that it can make more money if the public is blindly betting one side more than the other.

Line Movement Example

When more bets and more money come in for one side, oddsmakers need to make the opposite side more appealing. Sometimes that means moving the line. Imagine the following line moves for an NBA matchup:

  • Opener: Celtics -6 vs Bulls +6
  • 2 Days before the game: Celtics -6.5 vs Bulls +6.5
  • 1 Day before the game: Celtics -7.5 vs Bulls +7.5

The Boston Celtics opened as a -6 point favorite over the Chicago Bulls. Gamblers realized it was likely the Celtics would win by 6, so they jumped on a favorable opening line.

2 days before the game, the sportsbook realized they were overexposed to a Celtics’ victory. There wasn’t enough money on the Chicago Bulls to make a balanced market. So they decide to make a bet on the Bulls more appealing by posting a +6.5 spread. Now more money comes in for the Bulls, but not as much as the sportsbook needs.

A day before the game, the sportsbook moves the line again, this time giving the underdog Bulls a +7.5 line. That also means the Celtics need to win by -7.5, more challenging than covering the initial -6 point line. This change coaxes gamblers to back the Bulls now that they have more room for error.

With the point spread market more balanced, it’s time to see if there’s an opportunity to fade the public. If the public’s money is behind the Celtics, here’s a ripe opportunity to bet against them. The Bulls now have a comfortable +7.5 spread, which is probably more points than they need to cover.

A smart handicapper will swoop in and take the Bulls at +7.5.

FAQs on Sports Betting Line Movements

What causes sports betting line movements?

Common reasons why sports betting lines move include balancing action, a bad opening line, sharp money bets, star player injury or absence, outdoor weather conditions, and hype, marketing efforts, or extreme sentiments.

What makes a sportsbook move a line?

Sportsbooks want to balance their action as much as possible. A lopsided market in favor of one side means the sportsbook needs to make the other side more appealing. Balancing their action minimizes risk. Whether the line accurately represents the game’s outcome doesn’t matter, though it will often be representative of the final result.

When do sports betting sites release opening lines?

The opening line is the first line a sportsbook offers for a particular matchup. Opening lines for NFL and College football could be released up to a week before a matchup, though some lines may come out many weeks or months in advance. For the NBA, MLB, and NHL, sportsbooks will release opening lines after each team has concluded the game preceding their upcoming matchup.

Does a game’s opening line always equal it’s closing line?

The opening line value doesn’t always equal the closing line value. That’s because sports betting lines will frequently move multiple times before the matchup begins. It’s not uncommon to have a line move every 1-2 hours, particularly before a major sporting event.

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Sports Betting Resources

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  • Parlay Card Betting – Parlay cards are issued by major sportsbooks midweek, allowing bettors to make multiple point spread, total, and prop bet selections that can return big payouts. Not to be confused with an “off the board” parlay!
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