ERA Calculator
Enter a pitcher's earned runs and innings pitched to get the Earned Run Average — the number of earned runs allowed per nine innings, where lower is better.
The classic pitching stat
Enter earned runs and innings pitched and the calculator returns the Earned Run Average (ERA), scaled to a full nine-inning game.
Earned runs only
Use earned runs, not total runs — runs that scored because of an error are unearned and are left out of ERA.
What is ERA?
Earned runs allowed per nine innings
The ERA calculator turns two simple counts — the earned runs a pitcher has allowed and the innings they have pitched — into Earned Run Average, the single most quoted measure of pitching performance. ERA expresses how many earned runs a pitcher gives up over a standard nine-inning game, so it lets you compare a starter who threw 200 innings against a reliever who threw 60 on the same scale. Because it counts only earned runs, it tries to isolate the pitcher's own contribution from runs that scored because of fielding errors.
Enter earned runs and innings pitched to get the Earned Run Average instantly — and remember that a lower ERA is better.
ERA multiplies the earned runs by nine and divides by the innings pitched, which scales the runs allowed up to a full nine-inning game.
ERA = (earned runs × 9) / innings pitchedThe multiply-by-nine step is what makes ERA a per-game rate rather than a raw total. Innings pitched are recorded in thirds, so a partial inning shows as a decimal — 7.1 means seven and one-third innings and 7.2 means seven and two-thirds. ERA itself is dimensionless: it is simply a count of runs per nine innings.
Suppose a starting pitcher has allowed 40 earned runs across 180 innings on the season.
Multiply earned runs by nine
40 × 9 = 360 — the earned runs scaled to a nine-inning rate.
Divide by innings pitched
360 / 180 = 2.00 — the earned runs allowed per nine innings.
Read the ERA
The ERA is 2.00, meaning the pitcher gives up two earned runs per nine innings on average — an excellent, well below-league mark.
ERA reads as runs allowed per nine innings, so unlike most stats a lower number is better. As a rough guide, an ERA under 3.00 is elite, the high 3s to low 4s sit around league average for a typical season, and figures above 5.00 mark a struggling pitcher — though the exact thresholds drift with the era of play, the ballpark, and the league's overall run environment. A 2.00 ERA means the pitcher surrenders, on average, two earned runs every nine innings they throw; a 4.50 ERA means four and a half. Because it is a rate, ERA lets you line up pitchers with very different workloads, but it rewards sustained low scoring over a large sample — a single rough outing moves a season ERA far less than it moves a single-game one.
ERA is the standard headline number, but a couple of points are worth keeping in mind.
Fielding, luck, and decimal innings
ERA does not cleanly separate a pitcher from their defense: the official scorer decides which runs are earned, and balls hit at fielders or into a spacious ballpark can flatter the number. It also says nothing about how runs were prevented, so modern analysis pairs it with stats like FIP and WHIP. When you enter innings pitched, use the decimal convention — .1 is one-third of an inning and .2 is two-thirds, not tenths.