The odds-makers of NFL decide on the point spread, which is a number and it is then passed on to the sports book. Once this is done, the sports book offers the number to the public (betting people) who then decides to either go with the underdog or the favorites. The reason why point spread is derived is based on the idea of the public betting approximately same amounts for both teams. This rarely happens. Quite obviously, people bet more on the favorites.

A typical point spread looks like: Team A +7.5 -110 and Team B -7.5 -110. '+' meaning underdogs and '-' meaning favorites. The number with the '+' are the points given to a team's final score. You add the point spread to the team's final score. If your team has more points after this addition, you have won! If you opt for the favorites, you simply subtract the point spread from the final score. The -110 next to each of the teams shows the betting amount in order to win $100.

The main purpose of the point spread in a football game is to balance the chances of the teams in terms of betting. One team can be better than the other. However, that makes the weaker team no less a competitor in betting. The point spread equals the wager so that even bettors have equal chances.