The point-spread is a value that bettors must add or subtract from their team’s score when they place an even-money sports bet. Favorites have negative point spreads, and underdogs have positive point spreads. Each football game is usually handicapped by a point spread, where one team is favored over the other which is the underdog. For example:

Cowboys +4
Cardinals -4

If you bet on the Cowboys, they must win by more than four points for you to win your bet. If you bet on the Cardinals, they must either win the game, or lose by three or less points for you to win your bet. If the difference is four points, say 27-23 Cowboys win, then the bet is a push and all money is returned.

Think of the Cardinals as starting with a four-point head start, or just add four points to the Cardinal's final score. If the actual final score is Cowboys 15 – Cardinals 12, then for gambling purposes the score would be Cardinals 19 – Cowboys 18. Underdogs don’t always win the actual game, but they win about 60% of the time when a point spread is factored in.

Every sports book assigns its own initial point spread, also known simply as the spread or the line (not to be confused with the money lines) to each game before it’s played. The big books have their own handicappers; other books subscribe to line-making services. There is no single official point spread, although most casinos tend to be within a point or two of each other.