Remember most NFL bets against the points spread are minus-110, which means a bettor must wager $110 to win $100. Some sites and some games differ, you could get -105, or the other way at -120. So in order to calculate what you won (hopefully), or what you loss (hopefully not) you must factor in those odds. If a bettor made three bets on a Sunday and all three were -110 and he won two games and lost one, his or her net profit would be $90. The two wins would generate $200 minus the $110 for the loss.
Now, the other type of bets are money line bets. In those, the odds vary greatly. If you’re betting the favorite on the money line it could be as much as -300, or some times even -400 if the team is a prohibitive favorite. Conversely, if you bets the underdog you could get odds of +160 or even as high as +280. So in calculating your winnings there, you would just simply add the games you won (with the odds) and subtract the game you lost. Example: You won with a minus -300 favorites, won with a +160 underdog and lost with a minus -260 favorites. You would break even for the day. Your two wins would get you $260, but your loss would be $260.