Power ratings are numbers that estimate how strong each team is. They're one of the main tools oddsmakers and analysts use to set lines. If you've ever wondered how a spread like -6.5 gets created, power ratings are a big part of the answer.
The basic idea
A power rating gives each team a number, usually expressed in points. The difference between two teams' ratings estimates how much better one is than the other on a neutral field.
Example ratings:
- Team A: +8
- Team B: +3
- Team C: -2
On a neutral field:
- A vs B: A favored by 5
- A vs C: A favored by 10
- B vs C: B favored by 5
Then you add home advantage. See home-field advantage.
Worked example: building a spread
Team A (+8) hosts Team B (+3). Home advantage is estimated at 2 points.
- Rating difference: 8 − 3 = 5
- Plus home advantage: 5 + 2 = 7
- Projected spread: A -7
If Team B hosted instead:
- 5 − 2 = 3
- Projected spread: A -3
Then adjust for factors like injuries, rest and weather. If Team A's starting quarterback is out and that's worth 4 points, the projected spread at A's home becomes A -3.
Where ratings come from
There are many ways to build power ratings:
- Point differential. Teams that outscore opponents by more are usually better. Simple but effective.
- Adjusted for opponents. Beating strong teams counts more than beating weak ones.
- Efficiency stats. Points or yards per play, points per possession, shot quality and similar measures.
- Market-based. Some people reverse-engineer ratings from the betting lines themselves.
- Elo-style systems. Ratings update after every game based on the result and how surprising it was.
Professional ratings blend several of these, plus information about players and injuries.
A simple Elo-style idea
Elo systems, originally designed for chess, are popular for sports. The concept:
- Each team has a rating.
- Before a game, the ratings predict a win probability.
- After the game, the winner gains points and the loser loses the same amount.
- An upset moves ratings more than an expected result.
Worked example: a strong team beats a weak team as expected, and ratings move only a little. If the weak team wins, ratings move a lot, because the result was surprising. Over many games, ratings settle near each team's true strength.
Turning ratings into probabilities
A spread from power ratings can be converted to a win probability using historical relationships. Roughly, in the NFL, a 3-point favorite wins around 58-60% of the time and a 7-point favorite about 75%. In the NBA, the relationship differs because scoring is higher. See basketball odds and football odds.
Why your ratings vs the market matters
If your power ratings produce a spread of -7 and the market says -4, you have two possibilities:
- You know something the market doesn't, or weighted something better.
- Your ratings are missing something.
More often than not, it's the second one. Markets combine a lot of information. But comparing your numbers with the market is a great way to learn. When you differ, ask why.
Strengths of power ratings
- Consistency. They force you to be systematic instead of emotional.
- Objectivity. They reduce bias toward favorite teams.
- Speed. Once you have them, you can project every game quickly.
Weaknesses
- Matchups. Ratings measure overall strength, not specific matchups. A team might be strong overall but vulnerable to a specific style. See how to read a matchup.
- Injuries. Ratings based on past games may not reflect a key player's absence.
- Small samples. Early in a season, ratings are noisy.
- Overreacting. Updating too much after one result makes ratings unstable.
Building a simple rating yourself
A beginner-friendly method:
- For each team, take average points scored minus average points allowed per game.
- Adjust slightly for the strength of opponents faced.
- Shrink extreme values toward average early in the season (teams rarely stay as extreme as their first few games suggest).
- Add home advantage for the home team.
Compare your projected spreads with the market. Note where you differ, then check the results over a season.
Ratings in different sports
- NFL and college football: ratings in points, with key numbers in mind.
- NBA: ratings in points, adjusted heavily for player availability.
- MLB: team ratings matter, but the starting pitcher must be factored in separately.
- NHL: ratings help, but goalie choice and randomness are big factors.
- Soccer: ratings often expressed in goals or as probabilities for home, draw and away.
Practice with your own ratings
Creating simple power ratings and comparing them with the market is one of the best learning exercises in sports predictions. Use them to make free play-money picks on MockSport, and track how your projections perform. Start on the odds page.
FAQ
What is a power rating?
A number estimating how strong a team is, usually in points. The difference between two teams' ratings, plus home advantage, gives a projected spread.
How do oddsmakers use power ratings?
They use them as a starting point for lines, then adjust for injuries, rest, weather, matchups and market activity.
Are power ratings accurate?
They're useful but imperfect. They work best combined with up-to-date information about players and conditions.