How To Unlock Football Betting Value With ‘Key Numbers’

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The most important decision facing football betting fans each weekend is whether to take or lay the points. On the other side of the counter, the most critical determination for sportsbooks is if and when to move that number.

Occasionally, these two disparate but linked disciplines conspire to offer bettors the potential for a betting windfall. So how do you make the key numbers work in your favor? Let's take a closer look.

How The Betting Lines Move Around

Most sportsbooks will move a football line only after the maximum amount of money, an arbitrary figure called a ‘game limit,' is reached on one side of a particular point spread. Once that limit is achieved, the line is adjusted to attract action on the other side.

Let's say the Chipmunks are 8-point favorites over the Groundhogs in the Rodent Bowl and the house's limit is $5,000. If $5,000 more is bet on the Chipmunks than the Groundhogs, most sportsbooks in that position will move the line from -8 to -8 1/2 or -9.

The risk of a bookmaker being middled–a situation where gamblers on both sides of a betting proposition win–is dependent on the likelihood of the game score coinciding with the game's point spread. Over the past decade, the likelihood of a game being won by eight points was about 2 percent. Thus, bookmakers who have reached their game limit can quickly flee from -8 to -9 with relative impunity.

Sounds simple right?

Not so fast. All people may have been created equal but all numbers weren't. Some numbers, 7, 4, 6, and especially 3, must be treated differently. These digits are known as ‘key numbers.'

How Books Avoid Getting Middled

Although individual sportsbooks determine their own threshold for betting pain, as a general rule of thumb, in order to avoid middles, most sportsbooks won’t move off a point spread of 7, 4, or 6 until approximately 150 percent of the house limit is reached.

So, if the house limit is $5,000, a majority of sportsbooks will wait until they are $7,500 out of balance before shifting off those lines. It takes roughly 200 percent or double the game limit ($10,000 in our example) for sportsbooks to move off a point spread of 3, the most revered number in football betting.

The reluctance of bookmakers to move off a key number such as 3 is founded in strong historical and statistical evidence. About 14% of NFL games–roughly one in every seven–are decided by a field goal. That means that if a bettor can lay 2.5 and take 3.5, he has a substantial edge over the house.

Modern operators of sportsbooks, who unlike many of their predecessors have been schooled in the mathematics of sports betting, know this too, of course, and often will go to tortured lengths, including employing a money line, to avoid moving off 3.

Examining Historic Data

In the first 12 weeks on the 2011 NFL season, 43 of 176 games (24.4 percent) closed with one team favored by three points over another. Interestingly, only Green Bay and New Orleans, the last two Super Bowl champions, have failed to play a game this year with a spread of three points. Carolina, Cincinnati and Tennessee each have played five games where the spread was plus or minus three and Buffalo, Denver, Kansas City, Minnesota, Pittsburgh, San Francisco and Washington each have played four games with a spread of three points. It’s safe to say, that while it may be increasingly difficult to find a 3-point middle, there are ample opportunities for a search.

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Finding a middle on any of the other key numbers, 7, 4 and 6, is easier but only about half as profitable. Over the past decade, games were decided by 7, 4 or 6 points about 7 percent of the time, apiece. Given the house edge of 4.55 percent inherent in every 11/10 bet, a punter either will have to be very patient or very lucky to show a profit betting those middles.

The Most Famous Middle

The most famous key number middle took place in the 1979 Super Bowl between the Steelers and Cowboys. Although Pittsburgh was a solid 4-point favorite across Nevada and most other legally licensed football betting jurisdictions, an industrious bettor could lay -3.5 on the Steelers with an illegal Dallas bookie or take +4.5 on the Cowboys with an unlicensed Pittsburgh bet taker.

Of course, we’re not advocating using illegal sources to place a football bet, especially when you can bet with confidence with offshore sportsbooks (see our Bovada review here).

What’s the bottom line for football betting practioners? If you can find a middle on 3, bet it. Middles on 7, 4 and 6 also are worth a gamble but the bettor's edge is small. Tempting as it may be, it's probably wise to pass on all other numbers.