Elo ratings are a relatively simple rating system originally developed by the physicist Arpad Elo to rate chess players. The system can be easily adopted to other head-to-head competitions, and that’s just what Nate Silver of fivethirtyeight.com did in 2014 when he extended the ratings system to football.
Elo ratings estimate each team’s skill level using only the final scores of previous games and the locations of each game. That skill level is translated into a points system where an average team has 1,500 points, and teams usually fluctuate somewhere between 1,300 and 1,700 points. The Cowboys for example are currently ranked 14th overall with a middling 1,517 Elo points.