ERA Calculator
Calculate a pitcher's earned run average. Enter earned runs and innings pitched using the standard baseball notation where .1 means one out and .2 means two outs, and get ERA scaled to a 9-inning game plus a quality rating.
Example: with Earned runs 3 · Innings pitched (e.g. 6.2 = 6 and 2 outs) 7 · Innings per game 9 → ERA: 3.86.
- True innings pitched7.00 innings
- QualityAround league average
Computed by the calculator below using its default values. Change any input to see your own numbers.
ERA = earned runs x 9 / innings pitched. Innings entered as 6.1 or 6.2 are read as 6 and one or two outs, so 6.2 becomes 6 and two-thirds innings.
What ERA measures
Earned run average answers a simple question: if this pitcher threw a full nine innings at their current rate, how many earned runs would they give up? You take the earned runs allowed, multiply by nine, and divide by innings pitched. Earned runs exclude runs that scored because of fielding errors, so ERA aims to isolate the pitcher's own contribution.
Because it is scaled to nine innings, ERA lets you compare a starter who threw 200 innings with a reliever who threw 60. A lower number is better - it means fewer runs cross the plate per game's worth of work.
The outs-as-thirds rule
Baseball measures partial innings in outs, and each inning has three. The box-score shorthand writes them after a decimal point: 6.1 innings means six full innings plus one out (six and one-third), and 6.2 means six and two-thirds. This tool converts that notation for you, so 6.2 is treated as 6.667 innings, not 6.2. Getting this right matters - using 6.2 literally would understate the innings and inflate the ERA.
How it’s calculated
ERA = earned runs x innings-per-game / innings pitched, with innings-per-game = 9 by default (use 7 for many softball or doubleheader formats). Innings pitched entered as a decimal are read in baseball notation: .1 = one out (one-third) and .2 = two outs (two-thirds); other decimals are used as entered.
ERA credits the pitcher only for earned runs; unearned runs from errors are excluded by the official scorer, which this tool relies on you to have already separated out.
ERA quality guide
| ERA | Rating |
|---|---|
| Under 2.50 | Elite / Cy Young contender |
| 2.50-3.50 | Very good, above average |
| 3.50-4.50 | Around league average |
| 4.50-5.50 | Below average |
| Over 5.50 | Struggling |
Bands reflect typical modern MLB norms; league-average ERA usually sits near 4.00-4.50. ERA = earned runs x 9 / innings pitched.
Common mistakes
- Reading 6.2 innings as 6.2 instead of 6 and two-thirds - always convert the outs.
- Including unearned runs; ERA counts only earned runs.
- Forgetting to scale to nine innings, which is the whole point of the stat.
- Comparing ERA across eras or ballparks without context - run environments shift.
Frequently asked questions
What is the ERA formula?
ERA = earned runs x 9 / innings pitched. It projects how many earned runs a pitcher would allow over a full nine-inning game at their current rate.
How do innings pitched like 6.2 work?
The decimal counts outs, not tenths. 6.1 is six and one-third innings and 6.2 is six and two-thirds, because each inning has three outs. This calculator converts that automatically.
What counts as an earned run?
A run that scores without the help of a fielding error or passed ball. Runs that only scored because of a defensive miscue are unearned and are left out of ERA.
What is a good ERA?
Under 2.50 is elite, 2.50 to 3.50 is very good, and roughly 4.00 to 4.50 is league average in modern MLB. Above 5.50 is a struggle.
Why use 9 innings in the formula?
Nine innings is a standard game, so scaling to it makes pitchers with different workloads comparable. For 7-inning games you can change the innings-per-game value.