The NFL's key numbers are 3 and 7. Bettors better understand them. – The Washington Post

First and foremost, you need to be familiar with the sport’s key numbers, which, in the NFL, are three and seven. That is, three points for every field goal and seven points for every touchdown that includes an extra-point kick. Yes, there are also two-point conversions, which can impact the score, but many NFL games still end with a score differential of three or seven.

Since 2015 — when the NFL moved extra-point attempts back from what was essentially a 20-yard field goal to a 33-yard attempt — 15 percent of regular season games have ended with a scoring margin of three points. This may sound small, but it represents the most frequent outcome by a significant amount. Ten percent finished with a differential of seven points. Six, 14 and 10 were the next most frequent point differentials, but none of those occurred even eight percent of the time.

This matters when considering point spread wagers. When looking at weekly betting lines, dial in on point spreads of minus-2.5, knowing that a three-point differential will get you the win if you bet on a victorious favorite. Conversely, an underdog with a plus-7½ point spread is more desirable than one getting 6½ points.

In fact, it’s more valuable to have a spread of +7½ even at a higher price (-120, meaning a bettor would win $100 for every $120 wagered) than it is to have +6½ at the cheaper cost of -110 (when a $110 bet wins $100). Why? Because significantly more games end with a seven-point margin of victory or less (48 percent of NFL games) than with a six-point margin of victory or less (39 percent). This implies you’re more likely to cash on the +7½ bet — and that the improved probability of winning offsets the extra cost.

You can also use a variation of a parlay bet called a teaser, in which bettors can move the point spread a fixed amount of points in their favor, generally 6, 6½ or 7 points. Using the 6-point variation as an example, a team favored by 7 becomes favored by 1, while an underdog getting 4 points now gets 10. The number of legs (wagers) in the teaser bet determines the odds of the parlay, and all of the wagers involved must win in order for the teaser bet to cash. Two-team teasers typically pay -120 and three-team teasers usually pay +160, although there is some deviation from that, so be sure to shop around to get the best price and odds. (The advice to shop around goes for any bet, really.) The prices below are available at many U.S. sportsbooks.

The most advantageous variety of teaser is called a Wong teaser, named after Stanford Wong, the author of the book “Sharp Sports Betting.” Wong’s strategy involves using the 6-point teaser to move past both key numbers of 3 and 7 by focusing on underdogs getting between 1½ and 2½ points, teased up to 7½ and 8½, and favorites giving between 7½ and 8½ points, teased down to 1½ to 2½. Since 2015, these line movements have resulted in bets covering an astounding 77 percent of the time, enough to provide value no matter how many legs you have in a teaser parlay.

Here’s the math behind that last point, and why many sharp bettors use Wong teasers as a part of their overall strategy. A generic two-team 6-point teaser pays -120, which implies a 55 percent probability the bet will cash. Since there are two events in this case, using the Wong teaser, each is implied to have a 74 percent chance of converting (.74 times .74 = .55). Remember, Wong’s strategy involves events that have been covering 77 percent of the time, giving you a small edge on each bet.

Before you scoff at those few percentage points, bear in mind that the house edge mostly ranges from three to four percent, making this a great value bet at the prices mentioned. Looked at another way, a two-team Wong teaser should carry a line of -144 (assuming a 77 percent chance each leg wins), but instead pays -120, providing a better payout for winners.

And getting better odds than the likelihood of the expected outcome is at the crux of any sports betting conversation. You always want the bet tilted in your favor as much as possible. These strategies obviously won’t guarantee you will win any bet, but by adhering to the guidelines above you should be able to put the odds in your favor more often than not, leading to more profitable wagers long term.