ERA Calculator (Baseball)

Calculate a pitcher's Earned Run Average (ERA) based on earned runs and innings pitched. This essential baseball statistic helps evaluate pitching performance.

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By Sports/Athletic Editor | Published: Oct 23, 2025 | Reviewed by: Sports/Athletic Editor

Calculate ERA

Total number of earned runs allowed by the pitcher
Use decimals for partial innings (e.g., 5.1 = 5⅓ innings, 5.2 = 5⅔ innings)

How It Works

The Earned Run Average (ERA) is calculated using the formula:

ERA = (Earned Runs × 9) ÷ Innings Pitched

The formula multiplies the earned runs by 9 (the number of innings in a standard game) and divides by the total innings pitched. This standardizes the statistic to show how many earned runs a pitcher would allow over a full 9-inning game.

Understanding ERA

What is ERA?

Earned Run Average (ERA) is one of the most important statistics in baseball for evaluating pitcher performance. It represents the average number of earned runs a pitcher allows per nine innings pitched.

ERA Rating Scale

  • Below 2.00: Outstanding - Elite, Cy Young caliber
  • 2.00-3.00: Excellent - Top-tier starting pitcher
  • 3.00-4.00: Good - Above average pitcher
  • 4.00-5.00: Average - Solid major league pitcher
  • 5.00-6.00: Below Average - Needs improvement
  • Above 6.00: Poor - Struggling performance

Partial Innings

In baseball statistics, partial innings are expressed in thirds:

  • X.0 - Complete innings only
  • X.1 - Complete innings plus 1 out (⅓ inning)
  • X.2 - Complete innings plus 2 outs (⅔ inning)

Example Calculation

Scenario: A pitcher has allowed 10 earned runs over 45 innings pitched.

Calculation:

  • Earned Runs = 10
  • Innings Pitched = 45
  • ERA = (10 × 9) ÷ 45 = 90 ÷ 45 = 2.00

Result: The pitcher has an ERA of 2.00, which is considered excellent.

Tips & Notes

  • Earned vs. Unearned Runs: Only earned runs count toward ERA. Runs that score due to errors are unearned and don't affect a pitcher's ERA.
  • Context Matters: ERA can be influenced by factors like ballpark, defense quality, and league average. Consider ERA+ for park-adjusted comparison.
  • Sample Size: ERA becomes more meaningful with more innings pitched. A small sample size can lead to misleading numbers.
  • Relief Pitchers: Closers and relief pitchers typically pitch fewer innings, so their ERAs can be more volatile.
  • Historical Context: League-average ERA has varied throughout baseball history. A 3.50 ERA might be excellent in a high-scoring era but average in a pitcher-friendly era.

Frequently Asked Questions

ERA stands for Earned Run Average. It measures the average number of earned runs a pitcher allows per nine innings pitched. It's calculated by multiplying earned runs by 9 and dividing by innings pitched.

ERA = (Earned Runs × 9) ÷ Innings Pitched. For example, if a pitcher allows 10 earned runs in 45 innings, their ERA is (10 × 9) ÷ 45 = 2.00.

Generally, an ERA below 3.00 is excellent, 3.00-4.00 is good, 4.00-5.00 is average, and above 5.00 needs improvement. Elite pitchers often have ERAs below 2.50.

Earned runs are scored due to hits, walks, or hit batters. Unearned runs score due to defensive errors and don't count against the pitcher's ERA.

Partial innings are expressed in thirds. For example, 5.1 innings means 5 full innings plus 1 out (1/3 of an inning), and 5.2 means 5 innings plus 2 outs (2/3 of an inning).

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