Adjusted ERA+ Calculator

Adjusted ERA+, commonly abbreviated to ERA+, puts a pitcher’s earned run average in context by correcting for the hitter friendliness of his ballpark and the run-scoring environment of the league.

A score of 100 is league average; every point above or below is a percentage point better or worse than average.

This simple tool lets you convert raw ERA into the park and league adjusted ERA+ figure used by analysts.

Similarly, hitters are evaluated using a comparable statistic known as OPS+, which stands for on-base plus slugging percentage adjusted for park factors and league averages.

The adjusted OPS plus formula provides insight into a player’s overall offensive contribution by factoring in the conditions they face.

By comparing OPS+ values, analysts can effectively gauge a hitter’s performance relative to their peers in similar environments.

Adjusted ERA+ FAQ

What does a 100 ERA+ mean?

A score of 100 indicates that the pitcher performed exactly league average after accounting for park effects and run environment.

How is park factor used in the calculation?

The park factor is divided by 100 to create a multiplier.

Parks that suppress scoring (below 100) increase ERA+, while hitter friendly parks (above 100) decrease it.

Is a lower ERA always better than a higher ERA+?

Not necessarily.

ERA ignores context.

A pitcher with a slightly higher ERA may still own a better ERA+ if he plays in an extreme hitters park or a high scoring league.

Why do I need league ERA for a single season?

League ERA captures the overall scoring climate for that year.

Using it normalizes performance so ERA+ can tell you how the pitcher stacked up against his peers.

Can ERA+ be compared across different eras?

Yes.

Because ERA+ adjusts for league scoring levels it allows meaningful comparisons between pitchers from dead-ball seasons and modern high offense eras.