How the MLB Ratings Work
Methods and limits behind the Pascal Rating for MLB, which rates all 30 teams from regular-season runs scored and allowed.
Published by Pascal Institute. Edited by Christopher Merry, Chief Decision Scientist.
- What the rating measures
- The formula
- Expected wins
- Which games count
- Interpretive limits
- Sources and data
What the rating measures
The rating summarizes how well a team scored and prevented runs over the regular season, compared with the league as a whole. Over a full season, run differential is widely regarded as a steadier guide to team quality than win-loss record, because close games and bullpen timing add noise to the standings.
The formula
| Component | Definition |
|---|---|
| League rate | Total runs scored ÷ total team-games, across all 30 teams |
| Offense | 100 × runs scored per game ÷ league rate |
| Defense | 100 × league rate ÷ runs allowed per game |
| Rating | offense + defense − 100. A team that scores and allows exactly the league rate rates 100. |
Defense here means run prevention by the whole team: pitching and fielding together.
Expected wins
Each team also gets a Pythagorean expected winning percentage, runs scored^1.83 ÷ (runs scored^1.83 + runs allowed^1.83), multiplied by games played to give expected wins. The gap between actual and expected wins shows how far a team's record ran ahead of or behind its run totals.
Which games count
Only regular-season games count. Spring training, the All-Star Game and every postseason round are excluded, so the rating does not change during the playoffs. For that reason MLB is published as a season summary after the regular season rather than weekly through October.
Interpretive limits
No opponent adjustment. A team in a weak division plays easier opponents and can look better than it is.
No ballpark adjustment. Hitter-friendly parks inflate both runs scored and runs allowed for the home team, so offense and defense are each shaded by home park, even when the overall rating is less affected.
No roster or recency information. A team that changed its rotation in July is rated on its whole season, and injuries are not modeled.
It is a summary, not a postseason forecast. Short playoff series turn on starting pitchers, bullpen use and a few swings, none of which the rating sees.
Live ratings
Every team's current rating, updated as games finish, is on the MLB Team Ratings page.
Track record
See how the ratings have been scored in public, season by season and in retrospective studies, in the Track Record.
Sources and data
- AnalytIQ MLB Team Rating, methodology mlb-team-ratings-raw-v1: the formula and the Pythagorean exponent of 1.83.
- Season totals: AnalytIQ published rating batches and the AnalytIQ MLB game catalog, exported with read-only queries. Each summary's data file is kept with the published pages, and the build script checks that it reproduces the published ratings before adding any games.