By Zencalcy Editorial TeamLast reviewed About us
Earned run average estimates how many earned runs a pitcher allows per nine innings. This calculator converts baseball innings notation to outs first, so 6.1 means six and one-third innings, not six point one.
Convert earned runs and innings into a two-decimal ERA.
outs = full innings × 3 + outs digit innings = outs ÷ 3 ERA = 9 × earned runs ÷ innings
Baseball notation is not decimal: 6.1 is 19 outs and 6.2 is 20 outs. The formula uses outs so partial innings are counted exactly, and it ignores unearned runs because the name says earned.
| Symbol | Meaning |
|---|---|
| ER | Earned runs allowed, excluding runs that score because of an error or passed ball. |
| IP | Innings pitched in baseball notation, where the digit after the decimal counts outs. |
| outs | Full innings times three plus the outs digit, used to measure partial innings exactly. |
| ERA | Earned runs scaled to a nine-inning game, shown to two decimals. |
6.1 innings is 6 full innings plus 1 out, or 19 outs, which is 6.333 innings. ERA = 9 × 3 ÷ 6.333 = 4.26.
ERA, or earned run average, is earned runs allowed multiplied by nine and divided by innings pitched. It answers how many earned runs a pitcher would allow in a nine inning game at the current rate. Only earned runs count, meaning runs that would have scored without a fielding error or passed ball are excluded by the official scorer.
Innings are written in baseball notation, so 6.1 means six and one third innings and 6.2 means six and two thirds, not six point one or six point two. A calculator must convert that notation to a true decimal before multiplying by nine, or the answer will be wrong.
ERA depends on the fielders behind the pitcher and on the ballpark, neither of which the pitcher controls alone. A pitcher with a weak defense or a hitter friendly park will show a higher ERA even for identical pitching, and earned run classification involves scorer judgment, which adds another layer of noise to the figure.
Continue with the Fielding Percentage Calculator, On-Base Percentage Calculator, or the OPS Calculator — or browse more baseball tools and all sports calculators.
In baseball notation the digit after the decimal counts outs, not tenths of an inning. Three outs make an inning, so 6.1 is 6 and 1/3 innings and 6.2 is 6 and 2/3.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026