Key numbers – that’s one of those concepts that most sports bettors have heard of, but fewer understand what they are and why it is important. Key numbers are an important part of NFL and college football handicapping, and if you don’t ‘get’ them then you are working at a disadvantage. Let’s make sure we all understand them, shall we?

Key numbers in football deal with the margin between the number of points the winning team in a game scores and the points scored by the loser. Painfully obvious example – if the score in a game is 28-17 then the margin we are concerned about here is 11. Within reason pretty much any margin is possible in a football game – certainly any one or two digit margin. As expert sports handicappers know, there are some margins, though, that are considerably more common than others. The numbers that are the most common are called key numbers.

The most significant key number is three. In a study of 17 years worth of games, the winning margin was found to be three in 15.1 percent of the games played. Why is that? Well, think about how often a football game is tied until a team kicks a field goal in the closing seconds. Or how often teams trade points back and forth with only a field goal being the difference.

The second most common key number is seven. That margin obviously happens when a team wins by a touchdown. 7.1 percent of games finished at that number. For sports bettors, there are three other key numbers that happened with significant frequency, and each happened about the same amount of times – between 5.8 and six percent. Those numbers are six (two field goals, or an unconverted touchdown), four (the difference between a touchdown for one team and a field goal for the other), and 10 (a field goal and a touchdown difference).

It’s significant to note that when you add the frequency of those margins up you discover that about 40 percent of games finish with one of those five winning margins. Interesting, but how is it useful?

Key numbers – and three in particular – can tell you a lot about the psychology the odds makers use when they are thinking about a particular game. For example, if a line opens up with one team favored by 2.5 points books are basically daring people to bet on the favorite. By betting the favorite at tat line you have the key number of three on your side, so the winning outcome is more likely than it would be if the line was set at 3. While that is an opportunity when viewed in isolation I get very nervous when I see a line like that. If books aren’t afraid of taking action on a football team – if they are actively encouraging it in a case like this – then they have a good reason for that. If the favorite is a team that the public is likely going to like then I am going to be very cautious about backing that team – books don’t like to encourage you to make bets you have a good chance of winning. The same thing, though to a lesser extent, can be said about lines of -3.5, -5.5, -6.5, and -9.5. I’m not suggesting that I would absolutely never take a line of -2.5. I’m just saying that it sets off alarms and forces me, as a football handicapper, to really consider whether I am on the right side.

Key numbers are also important because once a line moves to a key number a book is very hesitant to move off of it. If, for example, a game opens at -2.5 but the action forces them to move it to -3 eventually. It will take far more action on the favorite than normal to force that line to move up another half point to 3.5 or beyond. There’s a very good reason for that – sportsbooks hate getting middled. Middling is a bet that let’s you earn 20/1 on your investment or more. If you take the favorite when the line is at 2.5 and then take the underdog when the line moves to 3.5 then you would win one bet and lose the other if the margin of victory was 1,2 or 4 or higher and your net loss would only be the juice on one bet – $10 if you had bet $100 on each side. If the game falls on the key number of three, though, then you would win both bets and make a $200 profit. Since the key number of three is hit about 15 percent of the time then over the long term when middling three you would lose $10 85 out of 100 times for a total loss of $850, but you would win $200 15 times for a total profit of $3000. That’s a net profit of $2150, with very little long term risk of doing anything other than make a healthy profit. Books hate losing money, and middling is a sure way for them to do that.

There are a couple of things to learn from that. First, if you get a chance to bet a middle on three do it. Second, if a game is at three it is very likely to stay there – especially if it didn’t open at three. To compensate for their unwillingness to move the line the sportsbooks will adjust the juice – charging -120 or -130 in stead of -110 to bet on the favorites. If you aren’t aware of this and careful to note what you are betting then you can unwittingly make a bet that seriously impacts your likelihood of profit – you have to win at a far higher rate to profit at -130 than you do at -110.

An understanding of key numbers can also fuel your decision making when it comes to the timing of your sports bet. If the team you like is at +2.5 then it might make sense to hold off on making your bet in the hopes that it will move to +3 and you will have the key number on your side – or at least not working against you. If your number is at -3 by the time you get to it but it didn’t start there then you’ll want to make your bet as soon as you feel comfortable to avoid having to pay too much to make the bet.

There’s one last interesting situation involving key numbers we’ll touch on here – the Wong teaser. These are football teasers in which the six point adjustment allows you to move through the key numbers of both 3 and 7. For example, if a game is at -8.5 then if you tease that game by six points it falls to -2.5 and the two biggest key numbers are now on your side. Those teasers were popularized a few years ago, and when you bet teasers with two or more games that fit the criteria it was found to be long term profitable. Sportsbooks didn’t like that much as you would expect, so now the combination of careful line placement and more expensive teasers has made it harder for football handicappers to capitalize on.