ERA Calculator (Earned Run Average)
Enter earned runs and innings pitched to calculate a pitcher's earned run average (ERA).
Earned run average (ERA) measures how many earned runs a pitcher allows per nine innings. Divide earned runs by innings pitched, then multiply by nine. A pitcher who gives up 3 earned runs in 7 innings has an ERA of 3 ÷ 7 × 9 = 3.86. Lower is better.
How to Use This Calculator
Enter the number of earned runs the pitcher allowed and the innings pitched. Because baseball innings are counted in thirds, enter the whole innings and then the extra outs — one out is a third of an inning, two outs are two-thirds. So 7⅔ innings is 7 whole innings plus 2 outs.
The calculator returns the ERA, the standard measure of a pitcher's run prevention, scaled to a full nine-inning game.
How the Calculation Works
ERA expresses earned runs on a per-nine-innings basis so pitchers who throw different amounts can be compared fairly. Dividing earned runs by innings pitched gives runs per inning, and multiplying by nine scales it to a complete game.
Only earned runs count — runs that score because of errors or passed balls are 'unearned' and excluded, because ERA is meant to measure the pitcher's own performance rather than the defense behind them.
ERA = (earned runs ÷ innings pitched) × 9
Worked Example
A pitcher allows 3 earned runs in 7 innings. Divide: 3 ÷ 7 = 0.4286 runs per inning. Multiply by nine: 0.4286 × 9 = 3.86.
So the ERA is 3.86. If those same 3 runs came in only 5 innings, the ERA would be 3 ÷ 5 × 9 = 5.40 — worse, because the runs were allowed in less time.
Assumptions and Limitations
- Uses earned runs only; unearned runs are excluded
- Innings are counted in thirds — use the extra-outs field for partial innings
- ERA does not capture defense, park effects or inherited runners
- A very small number of innings makes ERA swing wildly
Who Uses an ERA Calculator
Baseball and softball players, coaches, and fantasy managers use this to compute a pitcher's earned run average from earned runs and innings pitched. Run it to track a season, compare pitchers, or set a fantasy lineup. Enter the earned runs and innings to get the standard nine-inning ERA.
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Open calculator →Frequently Asked Questions
How do you calculate ERA?
Divide earned runs by innings pitched, then multiply by nine. Three earned runs in seven innings is 3 ÷ 7 × 9 = 3.86. It expresses run prevention per nine innings.
What is a good ERA?
It varies by era and league, but broadly, under 3.00 is excellent, around 3.00–4.00 is good, and above 5.00 is poor. Context like ballpark and league scoring matters.
What is the difference between earned and unearned runs?
Earned runs are charged to the pitcher; unearned runs score because of fielding errors or passed balls. ERA counts only earned runs so it reflects the pitcher, not the defense.
How do I enter partial innings?
Enter whole innings, then use the extra-outs field: one out is ⅓ of an inning and two outs are ⅔. So 6⅓ innings is 6 whole innings plus 1 out.
Why multiply by nine?
Because a regulation game is nine innings. Scaling earned runs to nine innings lets you compare starters and relievers who pitch very different amounts on the same basis.
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