How to Calculate ERA (Earned Run Average)
Earned run average, or ERA, is the headline number for any pitcher: the number of earned runs they give up per full game. It is the stat that decides who starts, who closes, and who leads the league. Here is exactly how it works, and the one difference between baseball and softball that trips people up.
4 min read · Reviewed July 2026
The ERA formula
ERA takes the earned runs a pitcher has allowed and scales them to a full game. In baseball a full game is nine innings, so you multiply earned runs by nine and divide by innings pitched.
ERA = (Earned Runs × 9) ÷ Innings Pitched
- ·Earned Runs: runs that scored without the help of an error or passed ball
- ·Innings Pitched: total innings the pitcher was on the mound
How innings pitched are counted
Innings pitched are written in thirds, because there are three outs to an inning. A pitcher who records one out past the sixth has thrown 6.1 innings; two outs past the sixth is 6.2. The decimal is outs, not tenths.
That matters when you divide. To do the math correctly, convert innings pitched to a true number first: 6.1 innings is 6 and one-third, or about 6.33; 6.2 is 6 and two-thirds, or about 6.67.
A pitcher allows 3 earned runs over 6.2 innings. That is 6.67 true innings. ERA = (3 × 9) ÷ 6.67 = 27 ÷ 6.67 = 4.05.
Softball ERA scales to seven innings
A regulation softball game is seven innings, not nine, so softball ERA scales earned runs to seven. Everything else is identical: same earned runs, same innings-in-thirds.
This is why the same line reads differently in the two sports. Three earned runs over six innings is a 4.50 ERA in baseball but a 3.50 ERA in softball. Use the wrong multiplier and every pitcher on the staff looks better or worse than they are.
Softball ERA = (Earned Runs × 7) ÷ Innings Pitched
What counts as a good ERA
Context sets the bar. At the highest levels a sub-3.00 ERA is excellent and anything under 4.00 is solid; in high-scoring amateur leagues those numbers run higher. Because ERA rewards a small sample, most leaderboards require a minimum number of innings pitched before a pitcher qualifies, so a single scoreless relief outing cannot top the board.
Key takeaways
- ERA = earned runs scaled to a full game, divided by innings pitched.
- Baseball multiplies by 9 innings; softball multiplies by 7.
- Innings pitched are counted in thirds (.1 = one out, .2 = two outs), so convert to a true number before dividing.
- Only earned runs count: runs that score on an error do not.
Frequently asked
What is the difference between ERA and earned runs?
Earned runs are a raw count of the runs a pitcher gave up without help from an error. ERA turns that count into a rate by scaling it to a full game and dividing by innings pitched, so pitchers with different workloads can be compared.
Why is softball ERA different from baseball ERA?
A regulation softball game is seven innings and a baseball game is nine, so softball ERA multiplies earned runs by seven instead of nine. The same pitching line produces a lower ERA number in softball.
Does an unearned run count toward ERA?
No. A run that scores because of a fielding error or passed ball is unearned and does not raise a pitcher's ERA, though it still counts on the scoreboard.
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