ERA+ Calculator
ERA+ takes a pitcher's ERA and indexes it to that season's league average, so a low-offense 1968 season and a high-offense 2019 season land on the same 100-centered scale. Enter your ERA, pick a season, and see your ERA+.
How your ERA+ compares
100 is league average by definition — where do you land
Why ERA+ instead of raw ERA
Raw ERA is easy to compute but hard to compare across seasons — a 3.50 ERA was merely average in the pitching-dominated late 1960s and excellent in the high-offense late 1990s. ERA+ fixes that by indexing your ERA to that season's league-average ERA, producing one number centered on 100. A pitcher with exactly league-average ERA always scores 100, whatever year it is — which is what makes ERA+ useful for comparing a 1968 season to a 2019 one.
How it’s calculated
ERA+ = 100 × (league ERA ÷ your ERA). Because a lower ERA is better, the league figure sits on top of the fraction — the opposite arrangement from a stat like OPS+, where a higher raw number is better. League ERA is published directly by Baseball-Reference for every MLB season from 1950 to 2025 (76 seasons), so every result on this page uses a real, directly published league average rather than an estimate.
This tool does not apply a park factor, which real ERA+ (as published by Baseball-Reference) does use to adjust for hitter- or pitcher-friendly home ballparks. Treat results here as a park-neutral estimate, not an exact match to a published ERA+ figure. Results are for context and entertainment, not a substitute for official league statistics.
Worked example
A pitcher with a 3.42 ERA in the 2019 season (league ERA 4.49, a high-offense year) scores an ERA+ of 131 — well above average. The exact same 3.42 ERA in the 1968 season (league ERA 2.98, the lowest-scoring modern season on record, sometimes called "The Year of the Pitcher") scores an ERA+ of only 87 — actually below average that year. Same raw number, a 44-point swing in ERA+, purely because the league context is so different.
Common mistakes
- Comparing raw ERA across different seasons instead of indexing to that season's league average.
- Forgetting that real, official ERA+ also applies a park factor — this simplified version does not.
- Assuming a lower ERA+ number is always better — unlike raw ERA, higher ERA+ is better (100 is average, above 100 is good).
Where it is used
- Comparing a modern starter's season to a Hall of Famer's from a lower- or higher-offense era.
- Quickly checking whether a raw ERA is actually good once league context is applied.
- Fantasy baseball, broadcast graphics, and sabermetric discussions that need an era-neutral pitching number.
Frequently asked questions
What counts as a good ERA+?
100 is league average by definition. Roughly 120 is a solid mid-rotation starter, 140 is an All-Star-caliber season, and 160 or higher is Cy-Young-caliber. Below 90 is below-average pitching for the era.
Why does the same 3.42 ERA score so differently in different seasons?
Because ERA+ measures ERA relative to that season's league average, not on an absolute scale. A 3.42 ERA in 2019 (league ERA 4.49, a high-offense season) is well above average and scores an ERA+ of about 131. The identical 3.42 ERA in 1968, the lowest-scoring modern season on record (league ERA 2.98), was actually below average and scores an ERA+ of about 87 — a 44-point swing on the exact same number, purely from league context.
Does this calculator adjust for ballpark?
No. Real, official ERA+ (as published by Baseball-Reference) multiplies by a park factor so hitter-friendly or pitcher-friendly home parks don't skew the number. This tool omits that step, so it is a simplified, park-neutral-assumption version — treat it as an estimate, not the exact figure you'd see on Baseball-Reference for the same pitcher.
Why is ERA+ inverted compared to something like OPS+?
Because a lower ERA is better (fewer runs allowed), ERA+ puts the league average on top of the fraction: ERA+ = 100 × (league ERA ÷ your ERA). A below-average (high) ERA produces a below-100 score, and an excellent (low) ERA produces an above-100 score — the opposite arrangement you'd use for a stat like OPS+ where a higher raw number is better.
Where does the league ERA data come from?
League-wide ERA is published directly by Baseball-Reference for every MLB season from 1950 through 2025, in its Major League Pitching Year-by-Year Averages table. This tool's season dropdown covers all 76 of those years, so every result uses a directly published league ERA rather than an estimate.