NFL betting how-to: Using team ratings to calculate point spreads
We've looked at the betting outlook for every team in the NFL, making a point to emphasize a key idea: The most important starting point for success in sports betting is understanding how the numbers you're betting into were created. If you're baffled by how one team is favored by a certain amount over another, then you're in big trouble.
NFL oddsmakers don't just make point spreads out of thin air each week. Even on Sunday nights, the first crack at the lines for the next week's games is just an adjustment from the lookahead lines that were widely available just days before. Before those, many sportsbooks had advanced "Game of the Year" lines for some or all of the season's games.
To come up with these point spreads, they used their ratings for each team and applied those numbers to a formula, then adjusted for an estimated home-field advantage. Sprinkle in a little logic about bettors' general preferences, and they can make final tweaks.
Once their best number is ready, they'll make it available for betting, at which point the market weighs in. If the market favors one side early, oddsmakers shift the point spread until that one-sided betting subsides. Over the week, bet limits will increase closer to game time, and oddsmakers will get more information on their number's fairness.
As kickoff approaches, bettors get their last chance to weigh in, but oddsmakers should've found a number they can work with. Throughout thousands of games, sportsbooks hope to profit thanks to the vig (or commission) that bettors are paying to make a safe and regulated wager - most often at -110.
Finding an edge on the market
Bettors can get the edge by beating the closing line. If a game we bet at -6.5 closes Cowboys -7, what would be a push on a Dallas 7-point win becomes a win for us. Those close wins help achieve our goal of winning at least 52.3% (the breakeven point on -110) of our bets.
How do we beat the market to valuable numbers? By having a good idea of what a point spread should be before it gets bet to that number, using past information from the betting market to determine what we expect the next point spreads to be. A simple rating system and a slightly more complicated formula is the easiest way to project that.
NFL team ratings
A rating system out of 100 points is a universally simple format. You're welcome to adjust your ratings in whatever way you evaluate teams. Do it by rating punters, for all I care.
However, we have a summer's worth of the market weighing in on how it values each team, thanks to regular-season win totals and lookahead point spreads for every game. Why not use that information to create "market ratings" as a starting point?
Point spread valuation/calculation
First, what's the longest possible point spread for an NFL game? The league that prides itself on parity averages about 10 possessions for each team, and even the biggest early blowouts usually have the leading team take the air out of the ball. In 2013, Peyton Manning led a historically potent offense against the notably terrible Jaguars. As a result, the Broncos were 28-point favorites - the longest spread in modern NFL history. They didn't cover, winning easily but not that easily, 35-19.
Until a team successfully covers a four-touchdown spread, we'll cap the largest possible point spread at just under that number, at 27 points.
From there, we'll take a team's rating out of 100 and multiply that percentage by 27 to give it a point rating. For example, the Chiefs' estimated rating of 75/100 from their offseason preview would give them 20.25 points. In the season opener, they face the Lions. Detroit's 58/100 rating makes it worth 15.66 points. That's a 4.59 difference between the two teams. However, the matchup is being played in Kansas City, and a 2-point home-field advantage would create a reasonable opening line of Chiefs -6.5.
|TEAM (Rating)||RATING x 27||DIFFERENCE||W/ HFA|
Some sportsbooks opened with that line, while others had an idea of what usually happens when the Chiefs play - they get bet. Moving the line to Chiefs -7 is a risk-free proposition. Either no one bets it anymore, and they've stopped the influx of Chiefs money coming in at -6.5, or they get enough money on the Lions to even it out. If they want to come off the key number of -7, they can do so replete with market information.
Whether it's your ratings, these market ratings, or my ratings, the goal is to be informed and ready for when a team's rating rises or drops after a high-profile win or loss.
Matt Russell is the lead betting analyst for theScore. If there's a bad beat to be had, Matt will find it. Find him on Twitter @mrussauthentic.