Elo rating
also: Elo · team rating · power rating
Our running team strength number: up after a win, down after a loss, by more when the result was a surprise.
Formula
expected = 1 / (1 + 10^(-(rating diff + home) / 400)); change = K x margin factor x (result - expected)Every final game updates both teams. Home field is worth 24 points, K is 4 (baseball is noisy, so ratings move slowly), and a bigger winning margin counts a little more. Between seasons every rating moves a third of the way back to 1500.
1500 is average, and a 100-point edge makes a team about a 64% favourite on a neutral field.
The common mistake
Elo does not know who is pitching. A team's rating on the day its ace starts and the day its fifth starter does is the same number.
Where to get it
Related
Elo rating from the API
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