What is ERA in Baseball?
Earned Run Average · Pitching
ERA, or Earned Run Average, measures how many earned runs a pitcher allows per nine innings pitched. It is the most widely used pitching statistic and reflects how difficult it is for opposing batters to score against a pitcher. Only earned runs — those scored without the benefit of fielding errors — count toward ERA.
Formula
ERA = (Earned Runs × 9) ÷ Innings Pitched
A pitcher who allows 3 earned runs in 9 innings has an ERA of 3.00. One who allows 3 earned runs in 6 innings has an ERA of 4.50.
Benchmarks
| Level | ERA |
|---|---|
| Elite | < 2.50 |
| Excellent | 2.50–3.00 |
| Above Average | 3.00–3.75 |
| Average | 3.75–4.50 |
| Below Average | > 4.50 |
ALL-TIME CAREER ERA LEADERS
| Rank | Player | ERA |
|---|---|---|
| 1 | Ed Walsh | 1.82 |
| 2 | Addie Joss | 1.89 |
| 3 | Jim Devlin | 1.90 |
| 4 | Jack Pfiester | 2.02 |
| 5 | Smoky Joe Wood | 2.03 |
| 6 | Mordecai Brown | 2.06 |
| 7 | John Ward | 2.10 |
| 8 | Christy Mathewson | 2.13 |
| 9 | Al Spalding | 2.13 |
| 10 | Tommy Bond | 2.14 |
BEST SINGLE-SEASON ERA IN MLB HISTORY
| Rank | Player | Year | Team | ERA |
|---|---|---|---|---|
| 1 | Dick Redding | 1917 | CAG | 0.82 |
| 2 | Tim Keefe | 1880 | TRN | 0.86 |
| 3 | Ferdie Schupp | 1916 | NY1 | 0.90 |
| 4 | Dutch Leonard | 1914 | BOS | 0.96 |
| 5 | Mordecai Brown | 1906 | CHC | 1.04 |
| 6 | Bob Gibson | 1968 | STL | 1.12 |
| 7 | Walter Johnson | 1913 | WSN | 1.14 |
| 8 | Christy Mathewson | 1909 | NY1 | 1.14 |
| 9 | Jack Pfiester | 1907 | CHC | 1.15 |
| 10 | Addie Joss | 1908 | CLE | 1.16 |
HISTORICAL CONTEXT
ERA was first adopted as an official statistic by the National League in 1912 and the American League in 1913, though it took decades before it became the primary measure of pitching performance.
The Dead Ball Era (1900–1919) produced extraordinarily low ERAs — Walter Johnson's career ERA of 2.17 reflects both his dominance and the lower-scoring environment of his time.
The "Year of the Pitcher" in 1968 saw Bob Gibson post an iconic 1.12 ERA for the St. Louis Cardinals, still the all-time single-season record for starters with sufficient innings. The following year, MLB lowered the pitching mound from 15 inches to 10 inches to restore offensive balance.
In the Steroid Era (late 1990s–2000s), league-average ERA climbed above 4.50 in some seasons, making sub-3.00 ERAs even more impressive. Modern analytics have supplemented ERA with FIP (Fielding Independent Pitching), which isolates what a pitcher directly controls.
ERA COMPARISON: HOW THE LEAGUE AVERAGE HAS SHIFTED
League-average ERA has varied dramatically across baseball history. A 3.50 ERA in 1968 was ordinary; the same mark in 2001 was excellent.
| Era | Years | Lg Avg ERA |
|---|---|---|
| Dead Ball Era | 1900–1919 | 2.89 |
| Live Ball Era | 1920–1941 | 4.14 |
| Post-WWII Era | 1942–1960 | 3.84 |
| Year of the Pitcher | 1961–1968 | 3.53 |
| Expansion Era | 1969–1988 | 3.78 |
| Steroid Era | 1989–2005 | 4.31 |
| Post-Steroid Era | 2006–2019 | 4.17 |
| Modern Era | 2020–2024 | 4.19 |
Figures represent MLB combined league-average ERA per era. Computed from Lahman historical MLB data.
FREQUENTLY ASKED QUESTIONS
What is ERA in baseball?
ERA, or Earned Run Average, measures how many earned runs a pitcher allows per nine innings pitched. It is the most widely used pitching statistic and reflects how difficult it is for opposing batters to score against a pitcher. Only earned runs — those scored without the benefit of fielding errors — count toward ERA.
How is ERA calculated?
ERA is calculated by multiplying a pitcher's total earned runs by 9, then dividing by their total innings pitched. This normalizes the stat to a per-nine-inning rate so pitchers with different workloads can be compared.
What is a good ERA in baseball?
In the modern era (post-2000), an ERA below 3.00 is considered elite, 3.00–4.00 is solid, 4.00–5.00 is average, and above 5.00 is below average. League-average ERA fluctuates by season and era — the 1960s "Year of the Pitcher" saw the American League average at 3.19 in 1968.
What is the lowest ERA in a single season in MLB history?
Tim Keefe posted a 0.86 ERA in 1880 (a short 12-game season), but among modern qualifying starters, Bob Gibson's 1.12 ERA in 1968 stands as the definitive record. Dutch Leonard's 0.96 ERA in 1914 is another landmark for the live-ball era.
What is the difference between ERA and FIP?
ERA measures all earned runs allowed, including those affected by the defense behind the pitcher. FIP (Fielding Independent Pitching) isolates the outcomes a pitcher fully controls — strikeouts, walks, hit batters, and home runs — to better estimate true pitching talent.
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