The NFL Spread Calculator is can offer spread bettors some insight when deciding if, and how many points to buy on the alternate line. This calculator uses over a decades worth of betting data to determine if buying a point under a given spread has paid off in the past. This is a very important point: this is not based purely on math, but on historical outcomes. The good news is that the data is a large enough sample that it is pretty trustworthy, but the bad news is that the NFL Spread Calculator is not an indicator of future outcomes. It also is not designed for NCAAF football since the scores vary wildly from the NFLs.
To use the NFL Spread Calculator, look at the basic spread the sportsbook is offering and then select the Alternate Spread you are interested in. Be sure you are using a sportsbook that offers alternate lines. The calculator will give you the expected odds and fair win percentage. Comparing those odds to your sportsbook will help you find value in certain spreads.