Calculate a baseball pitcher's Earned Run Average (ERA) by entering Earned Runs, Innings Pitched, and the Regulation Innings per Game (typically 9). You get back the pitcher's ERA value along with a performance rating so you can instantly gauge how effective a pitcher has been on the mound.
Earned Run Average (ERA)
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ERA Rating
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Earned Runs
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Innings Pitched
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ERA stands for Earned Run Average. It measures a pitcher's effectiveness by calculating how many earned runs they allow per nine innings pitched. Earned runs are runs that score without the help of fielding errors or passed balls. A lower ERA indicates a more dominant pitcher.
The ERA formula is: ERA = (Earned Runs ÷ Innings Pitched) × 9. For example, if a pitcher allowed 15 earned runs in 65⅔ innings, their ERA would be (15 ÷ 65.67) × 9 ≈ 2.06. The result is scaled to nine innings so performance can be compared across pitchers with different workloads.
In Major League Baseball, an ERA below 3.00 is considered excellent, 3.00–4.00 is good, 4.00–5.00 is average, and anything above 5.00 is below average. Elite pitchers often post ERAs under 2.50 during dominant seasons. Standards can vary by league level and era of play.
Earned runs are runs that score as a direct result of the pitcher's performance — hits, walks, and home runs. Unearned runs result from fielding errors or passed balls that extend innings abnormally. Only earned runs are factored into ERA, making it a fairer measure of the pitcher alone.
Partial innings are recorded in thirds: one out = ⅓ inning, two outs = ⅔ inning. When entering innings pitched into this calculator, convert thirds to decimals — for example, 65⅓ = 65.33 and 65⅔ = 65.67. Using the correct decimal ensures your ERA calculation is accurate.
An ERA of 0.50 means the pitcher is allowing just half an earned run per nine innings pitched — an extraordinarily dominant performance. This level of ERA is rarely sustained over a full season and would place the pitcher among the greatest pitching seasons in baseball history.
A lower ERA is always better. Since ERA measures how many earned runs a pitcher allows per nine innings, fewer runs allowed means a more effective pitcher. A pitcher with a 2.00 ERA is giving up half as many earned runs per game as one with a 4.00 ERA.
The same formula applies — ERA = (Earned Runs ÷ Innings Pitched) × Regulation Innings. For a 7-inning softball or minor league game, you would use 7 instead of 9. This calculator lets you change the regulation innings per game to handle any league format.