ERA calculator
Enter earned runs and innings pitched the way a box score writes them (6.1 means 6⅓ innings) and this ERA calculator gives earned run average to two decimals. Switch to 7 innings for softball and high school, or add up several games at once.
ERA calculator tool
Add up several games
Enter each game or season line; totals use the game length chosen above.
| # | ER | IP | ERA |
|---|
How to use the ERA calculator
- Choose 9 innings for MLB, college and most adult baseball, or 7 innings for fastpitch softball and seven-inning high school games.
- Enter the earned runs charged to the pitcher.
- Enter innings pitched in box-score notation: 6 for six full innings, 6.1 for six and one out, 6.2 for six and two outs.
- Read the ERA, rounded to two decimals the way it is printed on a stat sheet. To combine games, fill in the table: the total ERA is worked out from all outs and earned runs together, not by averaging each game's ERA.
The ERA formula
ERA = 9 × earned runs ÷ innings pitched
Earned run average answers one question: how many earned runs would this pitcher allow over a full nine-inning game? A run is earned unless it scored because of a fielding error or a passed ball; the official scorer decides by imagining the inning without the mistake. For seven-inning games, replace the 9 with a 7.
The tricky part is the innings. Because 6.1 means 6⅓ and not 6.1, the ERA calculator converts innings to outs first (6.1 = 19 outs), then uses outs ÷ 3 as the true number of innings. Typing 6.1 into a normal calculator gives the wrong answer.
Worked examples
- One start: 3 earned runs in 6.1 innings. 6.1 innings = 19 outs = 6.333 innings. ERA = 9 × 3 ÷ 6.333 = 4.263, shown as 4.26.
- A season: 60 earned runs in 180.2 innings. 180.2 = 542 outs = 180.667 innings. ERA = 9 × 60 ÷ 180.667 = 2.989, so 2.99.
- Softball: 3 earned runs in 6.1 innings over seven-inning games: 7 × 3 ÷ 6.333 = 3.32.
Why not average game ERAs? A pitcher with a 0.00 ERA over 7 innings and 9.00 over 1 inning has allowed 1 earned run in 8 innings, which is 1.13, not the 4.50 you would get by averaging the two numbers.
Earned or unearned? Two quick cases
- With two outs, the shortstop boots a routine grounder that should have ended the inning, and the next batter homers. Both runs are unearned: without the error the inning was over.
- A batter doubles, moves to third on a passed ball and scores on a sacrifice fly. If the scorer decides he would not have scored from second on that fly ball, the run is unearned; if he would have scored anyway, it is earned.
Unearned runs still count on the scoreboard and in the pitcher's runs allowed; they are just left out of ERA.
What is a good ERA?
ERA depends on the league, the ballpark and the era, so treat this table as rough context for modern MLB, not a rule. Recent MLB league-wide ERAs have been around 4.00.
| ERA (approximate) | Rough MLB context |
|---|---|
| Under 2.00 | Exceptional; rare over a full season for a starter |
| 2.00 – 2.99 | Excellent, ace-level |
| 3.00 – 3.99 | Above average |
| 4.00 – 4.49 | Around league average |
| 4.50 – 5.49 | Below average |
| 5.50 and up | Poor at the MLB level |
Youth, high school and softball numbers are not comparable with MLB: fields, pitching distances and defense are different. Compare pitchers in the same league and season.
Tips
- Over a handful of innings ERA swings wildly. One bad inning can double it, so look at innings pitched before judging.
- Keep score in outs if you track games by hand; converting to the 6.1 / 6.2 notation at the end avoids rounding mistakes.
- For hitters, use our batting average calculator, OPS calculator and slugging percentage calculator.
How we tested it
The ERA code runs against automated Node tests: 3 earned runs in 6.1 innings gives 4.26, 60 earned runs in 180.2 innings gives 2.99, 0 earned runs in 9 innings gives 0.00, and in seven-inning mode 3 earned runs in 7 innings gives 3.00 and in 6.1 innings gives 3.32. The innings parser is tested to read 6.1 as 19 outs, 6.2 as 20 outs and 0.1 as 1 out, and to reject 6.3, 6.5, negative numbers and text. Earned runs with zero innings show as infinite.
Frequently asked questions
Why can't I enter 6.3 or 6.5 innings?
In baseball notation the digit after the point counts outs, not tenths. 6.1 is six innings and one out, 6.2 is six innings and two outs, and the third out completes the inning, making it 7.0. So .3 and above never appear in a box score.
What ERA does a pitcher have with earned runs but no outs?
If a pitcher allows earned runs without recording an out, the ERA is infinite, because you would divide by zero innings. Box scores and stat sites show it as ∞ or INF. One out later, it becomes a (very large) normal number.
Is ERA the same in softball?
The idea is the same, but softball games are scheduled for seven innings, so the formula multiplies by 7 instead of 9. A softball pitcher who allows 3 earned runs in 21 innings has an ERA of 1.00, while in the 9-inning version the same line would read 1.29. Most high school baseball is also played over seven innings.
How many innings does a pitcher need to qualify for the MLB ERA title?
One inning pitched per game the team plays, so 162 innings in a normal 162-game season. Pitchers with fewer innings still have an ERA, they just do not appear on the league leaderboard.
Does a relief pitcher get charged for runners he inherits?
No. Runs are charged to the pitcher who put the runner on base. If a reliever enters with a runner on second and that runner scores, the run counts against the previous pitcher's ERA, not the reliever's.
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