Earned run average is 9 × earned runs ÷ innings pitched. Innings are counted in thirds, so 304.2 in a box score means 304⅔. Bob Gibson allowed 38 earned runs in 304.2 innings in 1968: 9 × 38 ÷ 304.667 = 1.12. For seven-inning high school or softball games, replace the 9 with 7.
Coaches keeping a scorebook, fantasy players checking a reliever, and parents tracking a youth pitcher all run into the same trap: innings pitched are written as 45.1 or 45.2, but those digits are outs, not tenths. Typing 45.2 straight into a formula understates the innings and inflates the ERA. Here you enter full innings and the extra outs separately, pick the game length your league plays, and get the ERA with the working shown, the innings as a true decimal, earned runs per inning and the total outs recorded. On a nine-inning scale the result is also placed against rough MLB benchmarks. One limit: the number is only as good as the earned-run call. Deciding whether a run would have scored without an error is the official scorer's judgment, and this page takes your earned-run count as given.
Count only runs charged as earned. Runs that score because of an error or passed ball stay out.
Type the whole innings in the first box and use the stepper for the digit after the dot: 0, 1 or 2 outs.
Keep 9 for MLB and college, or pick 7 or 6 for shorter regulation games.
The steps show the converted innings and the division, so you can match the figure against a published stat line.
Result Earned run average: 1.12
MLB benchmark: Excellent (under 2.50)
Innings as a decimal: 304.667
Earned runs per inning: 0.125
Outs recorded: 914
304.2 innings is 304⅔, not 304.2. Nine times 38 divided by 304.667 gives the 1.12 ERA that led to the lowered mound in 1969.
Result Earned run average: 1.53
MLB benchmark: Excellent (under 2.50)
Innings as a decimal: 276.667
Earned runs per inning: 0.17
Outs recorded: 830
9 × 47 ÷ 276.667 = 1.53, the lowest qualified National League ERA of the 1980s.
Result Earned run average: 2.00
MLB benchmark: Not rated (non-9-inning scale)
Innings as a decimal: 42
Earned runs per inning: 0.286
Outs recorded: 126
On a seven-inning scale, 7 × 12 ÷ 42 = 2.00 earned runs per full game.
ERA = G × ER ÷ IP, where IP = full innings + outs ÷ 3
ERAGERIPThe official rules define ERA as the earned runs a pitcher would allow over a full game at his rate so far: earned runs times nine, divided by innings pitched. Each out is one third of an inning, so 276.2 innings becomes 276.667 before dividing. The result is shown to two decimals, the way box scores and league leaderboards print it. For leagues that play seven or six innings, the multiplier changes to match, which keeps the figure on a per-game basis for that level.
Scorers record innings by outs. Each out is a third of an inning, and the digit after the dot counts outs past the last full inning. So 6.1 is 6⅓ and 6.2 is 6⅔; there is never a 6.3, because the third out completes the seventh inning.
A run is earned when it would have scored without help from a fielding error or a passed ball. The official scorer reconstructs the inning without the misplay; runs that would still have crossed the plate are earned and charged to the pitcher responsible for the runner.
League averages in recent seasons have mostly sat around 4.00 to 4.30. A starter under 3.00 over a full season is among the best in the league, while anything above 5.00 usually means a pitcher is fighting for a rotation spot. The benchmark line shown here uses broad bands around those levels.
In the live-ball era the standard reference point is Bob Gibson's 1.12 in 1968, over 304⅔ innings. Dutch Leonard's 0.96 in 1914 is lower, but it came in the dead-ball era with far less scoring league-wide.
If a pitcher allows an earned run without recording a single out, the division has zero innings and no finite ERA exists; box scores print it as infinite or as a dash. This page asks for at least one out so that the figure is always a real number.
ERA is meant to express runs per regulation game. High school baseball and fastpitch softball play seven innings, so their stat books multiply by 7. Using 9 there would inflate every pitcher's figure by about 29 percent compared with how their league reports it.
Using this tool in an assignment, article or report? Copy a citation, or a link for your website.
Tools Directory Editorial Team. (2026, October 22). ERA Calculator. Tools Directory. Retrieved October 26, 2026, from https://tools.milunir.com/sports/team-sport-statistics/era-calculator/
Tools Directory Editorial Team. “ERA Calculator.” Tools Directory, 22 Oct. 2026, https://tools.milunir.com/sports/team-sport-statistics/era-calculator/. Accessed 26 Oct. 2026.
Tools Directory Editorial Team. “ERA Calculator.” Tools Directory. Last modified October 22, 2026. Accessed October 26, 2026. https://tools.milunir.com/sports/team-sport-statistics/era-calculator/.
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