Betting Spreads in NFL – Key Numbers and Trends

Everyone who has ever successfully bet on NFL games has heard about key numbers. A key number is one that occurs more frequently than random chance would suggest.

The NFL has the most unique scoring system of any major sport. The scoring events in a football game are random and worth an arbitrary number of points. A field goal is worth three. A touchdown is worth six with the possibility of a seventh if the extra point is made. Unlike baseball, where each run is worth one, or even basketball where you have 1-, 2- and 3-point baskets, in football we tend to get scores that are multiples of a combination of the numbers of three and seven.

Therefore, based on the way the scoring system is set up, you will see a lot of games that fall on those key numbers that are multiples of those scoring events. The main key numbers we often hear discussed are three and seven. Numbers like 6, 9, 10, 13 and 14 are also multiples of number like 3 and 7 and sometimes referred to as semi-key numbers. The real question is how often do these key numbers and semi-key numbers come in to play? And how do we make money off this?

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NFL rule changes

Back before the turn of the century, the NFL was experiencing a dip in scoring. Scoring plays make things exciting. Exciting football means fans will pay to come see it and advertisers will pay to run ads while people are watching. With those motivating factors, the NFL changed rules to make it easier for wide receivers and tougher on handsy cornerbacks. High-end quarterback play is also correlated with points being scored. That is why the NFL put in special rules about when and how defensive players can hit a quarterback, including harsh penalties for crossing the line of what is and is not a legal hit. They also made changes to the way safeties can manhunt players coming over the middle of the field to make plays. Outlawing hits leading with the helmet and tighten up the rules on when contact can be made. All of these changes benefitted passing games at the expense of the run game, which had become the preferred way to move the ball at the time. 

Over the years, other changes in the rules also affected scoring. The addition of the two-point conversion in 1998 was one of those. More recently, the moving back of the extra-point distance from 2 yards to 15 yards was another. These are very important dates to know, because if you want to understand how key numbers have changed over the years, you have to be able to pinpoint the years where the rules changed. The changes mentioned in the paragraph above led to more scoring. More scoring means more multiples of 3 and 7, but also more potential for a missed extra point or a combination of touchdowns and field goals that lead to a final margin of victory that is not a multiple of those two numbers. The addition of the two-point conversion, the more recent moving back of extra-point distance, and the overall change in the analytical mindset of coaches going for two have also factored into the analysis of what numbers are still “key” numbers. 

What are key numbers in football

Below is a chart of all the winning margins from the 2020 NFL season, courtesy of FTNData. The higher the bar goes on the graph, the more often that number was the winning margin in NFL football games last regular season. The sample size is 256 games. 

As you can see from the chart, the number that was landed on most often was 3. The final margin of victory was exactly 3 points in just shy of 15% of NFL games last season. This is pretty much in line with what we see when we look at the different windows of games based on when the rules changed. Whether we go back to 2006, or even further back into the 1980s. In more recent times, the number has been hovering between 14.5% and 15.5%. It was about 1% higher 20-plus years ago, but even a look back to 1989 has 3 as a winning margin a little over 15% of the time.

This is and always has been the biggest key number in football and one that you should take note of. On a full week of NFL without any byes, we have 16 games. If 14-15% of those games are going to end with a final margin of 3, that equates to 2.5 games per week. This is why books are so hesitant to move a number from 2.5 to 3.5 or vice versa. They do not want to open themselves up to savvy bettors taking both sides of the number 3 and cashing both sides of that bet. A final score of exactly three points happens almost twice as often as any other final score and you can bet the sportsbooks know this chart well. This is why getting +3.5 or laying only -2.5 comes with a big advantage for bettors. Savvy players will take advantage of these opportunities when they arise.

The second-most key number in the NFL is 7, and this is interesting. A look back 15 years shows that 7 is becoming less of a key number. When looking back to 2006, we saw the number comes in just over 8.5% of the time. Last year, that number was under 8%. Is that a massive difference? Not really. But it is slightly less and probably has a lot to do with a missed extra point or a two-point conversion here or there. Over the course of the 256 games played, this is a difference of only one or two games. The reason I have strong convictions that the rules change is responsible for the lessened impact of the number 7 is that we also see an increase in the percentage of times 6 and 8 have fallen as a final score. In the early part of this century, the 6 came in about 5-6% of the time, but the final margin of 8 was less than 3% of games. Last season, the 6 was over 7%, but the 8 also saw a bump up to over 5%.

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Two things to remember here. The extra point is moved back, which means more misses. The other thing is that analytics have taken over the NFL thinking. A team down 14 points would normally have kicked an extra point to make that 7 and hope for another touchdown to tie the game. Now coaches are starting to go for two-point conversions to make it either 6 or 8. Therefore if they do not get the second touchdown, they need to tie it or take the lead, the final score is now one of the other numbers instead of the 7. This might not sound like a big deal to you, but it will be when it happens and you are holding a -6.5 or a +7.5 and the numbers land half a point outside of your range. I want to stress that that the change is not a major one, but it is one you need to be conscience of. While it might only be a difference of maybe one or two games per year from the early part of the century to today, that could have a significant impact on your winnings if you end up on the wrong side of that number in one or two more games. 

The last thing I want to mention here are the semi-key numbers of 6, 10 and 14. If you look back to 2000 you will see that those three numbers are the next-most landed-on final margins of victory. all about 6% of the time. Historically 10 lands more often than 6, which comes in more often than 14. It is tenths of a percentage point that differentiates these numbers and that is only a game difference here or there. Last year the 14-point margin actually came in more than the 6 or 10, but a one-year sample size is not enough to change anyone’s thoughts on this right now. All three of those are semi-key numbers that come in less often than 7 and half as often as 3, but still more often than any other winning margin. 

How to bet key numbers

Making money by using key numbers really comes down to remembering two things. The edge is always on the side of the key number where you would get the win. If you like a favorite, getting them at -2.5 instead of -3 is a big edge. If you like the underdog in a game, getting the +3.5 is what you would like to see. This way if the game happens to be one of the 15% of games that lands on that number, you would get the win. When we are talking about the number 7, the edge is not nearly as great. The 6 and 8 are starting to come in a bit more often for the reasons discussed and therefore getting -6.5 on a favorite or 7.5 on an underdog is not as important as it might have been in the past. You still would rather have the hook on your side whenever possible, but the edge is less than it is on the number 3. 

The second point I want to make for people who follow me is that this also affects teaser strategy. I love betting teasers during the NFL season. In a teaser you get to add or subtract 6 points from the spread. With 3 still being the most key number, getting a spread of -8.5 down below -3 is still a major thing to do. What is less appealing to me with the changes we see here is taking a spread of +1 or +1.5 and bumping it up to + 7 or +7.5. The edge on this “Wong Teaser” leg is still more than other numbers, but the less the 7 becomes a key number and the more often numbers like 6 and 8 become prevalent, the less the edge is on crossing those numbers. I will still do it when I think the situation calls for it, but if I have the option to take a number down from over a touchdown to under a field goal, I will do that 99 times out of 100 instead of taking it up to 7 or 8 from 1 or 2. 

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