Point spreads

Reading a spread

Take a favorite at −3.5 and the underdog at +3.5:

• The favorite covers by winning by 4 or more.
• The underdog covers by losing by 3 or fewer, or by winning the game.

The half point means one side always covers. On a whole-number spread such as −3, a 3-point win lands exactly on the line: that is a push, and both sides get their stakes back.

The price on each side

Each side of a spread has its own price, usually close to −110. At −110 on both sides, each side implies 52.38%: that is the break-even win rate, not 50%, because the sportsbook's margin is built into both prices.

The price moves as well as the line. A favorite at −3 (−120) with the underdog at +3 (+100) implies 54.55% and 50.00%, together 104.55%. With the margin taken out, the fair chances are about 52.17% and 47.83%. So the same −3 is a different bet at −110 than at −120: compare the price as well as the number.

When the line moves

Lines open, take bets and news, and move until kickoff. A move from −3 to −3.5 changes which final margins win and lose, and how much each half point is worth depends on how often games finish on that margin. In the NFL some margins come up far more often than others (see the NFL key numbers guide).

Alternate spreads

Many sportsbooks also offer alternate spreads: more points at a shorter price, or fewer points at a longer one. They are priced off the main line, with the margin built in again.