Point Spread

How a spread settles

A point spread adds points to one team’s final score, or takes them away, for settlement. If the favorite is −6.5, it must win by 7 or more to cover. The underdog at +6.5 covers by losing by 6 or fewer, or by winning outright.

Half-point spreads can’t push. A whole-number spread returns the stake when the margin lands exactly on the number.

The number and the price

A spread is meant to make both sides close to even propositions, so both are usually priced near −110, a 52.38% break-even rate. When a book wants to adjust, it can move the number or change the price: −3 at −110 and −2.5 at −125 are two ways of quoting nearly the same opinion. Always compare the number and the price together.

Alternate spreads let you choose a different number at a different price. A bigger head start for the underdog costs more; laying more points with the favorite pays more.

Key numbers in football

NFL games don’t end at random margins. Because most scoring comes in three- and seven-point units, exactly 3 has historically been the most common final margin, at around 15% of games, with 7 next. That makes the half points around 3 and 7 the most valuable on the board.

Moving from −3.5 to −3 turns a loss on a three-point win into a push; moving from −3 to −2.5 turns that push into a win. Moving from −5.5 to −5 changes the result only on a five-point margin, which is much less common. Basketball margins are spread more evenly, so key numbers matter far less in the NBA.

When buying a half point pays

Many books let you buy a half point at a worse price. Suppose you can take a favorite at −3 (−110) or at −2.5 (−125). Let W be the chance the favorite wins by 4 or more, and P3 the chance it wins by exactly 3. Moving to −2.5 turns P3 from a push into a win, but cuts the profit on every win from $0.909 to $0.80 per dollar staked. The change in expected value per dollar is 0.80 × P3 − 0.109 × W.

• With W at 45% and P3 at 9%, the buy adds about 2.3 cents per dollar staked.
• With W at 45% and P3 at 5%, it costs about 0.9 cents per dollar.

The buy only pays when the game is likely to land on the number you are buying onto. The half-point calculator runs this comparison with your own probabilities.

Spreads in other sports

Baseball and hockey use fixed spreads, the run line and the puck line, usually set at 1.5, with prices that move instead of the number. A favorite at −1.5 needs to win by two or more, so it is often priced at plus money. Basketball and college football spreads move by half points like the NFL’s, and the point spread calculator settles any spread bet from the final score.