Earned run average is baseball’s classic pitching statistic: the number of earned runs a pitcher allows per nine innings. It strips out runs caused by fielding errors and puts every pitcher on the same per-game scale, whether they threw 30 innings or 230. This calculator handles the awkward part — innings written in box-score notation like 185.2 — and also works for seven-inning high school and softball games.
How to use the ERA calculator
- Enter the pitcher’s earned runs allowed.
- Enter innings pitched as it appears in a box score: 7, 6.1 or 6.2. You can also type 6 1/3 or 6⅔.
- Choose the length of a regulation game: 9 innings (MLB, college), 7 (high school, softball) or 6 (many youth leagues).
The result shows the ERA to two decimals, the innings as a true decimal, total outs recorded and earned runs per inning, with every step written out below.
ERA formula
where ER is earned runs, IP is innings pitched as a decimal, and G is the number of innings in a regulation game (9 in professional baseball).
Converting innings pitched
Box scores write partial innings in thirds, using the digit after the point to count outs:
| Box score | Outs | Innings (decimal) |
|---|---|---|
| 6.0 | 18 | 6.000 |
| 6.1 | 19 | 6.333 |
| 6.2 | 20 | 6.667 |
| 185.2 | 557 | 185.667 |
A common mistake is treating 6.1 as 6.1 innings. Dividing by 6.1 instead of 6.333 makes the ERA too high. The calculator rejects values like 6.33 or 6.5 and asks for 6.1 or 6.2 instead.
Worked example
A starter allows 62 earned runs in 185.2 innings.
- Innings: 185 + 2/3 = 557 outs ÷ 3 = 185.667.
- ERA = 9 × 62 ÷ 185.667 = 558 ÷ 185.667 = 3.01.
In a 7-inning league the same numbers would give 7 × 62 ÷ 185.667 = 2.34, which is why ERAs from different game lengths should not be compared directly.
What counts as a good ERA?
League-wide ERA changes with the era of the game, so it is best judged against the league average. As a rough guide for modern major league starters:
| ERA | Rough rating |
|---|---|
| Under 2.00 | Elite, award-contending |
| 2.00–2.99 | Excellent |
| 3.00–3.49 | Very good |
| 3.50–3.99 | Above average |
| 4.00–4.49 | Around average |
| 4.50–4.99 | Below average |
| 5.00 and up | Poor |
Relief pitchers often post lower ERAs than starters because they face fewer batters and frequently enter mid-inning. For history buffs, the lowest single-season ERA of the live-ball era is Bob Gibson’s 1.12 in 1968 — a season so pitcher-friendly that the mound was lowered the next year.
Limits of ERA
ERA depends on the defense behind a pitcher, the ballpark, and on how the official scorer rules errors. Runners a reliever inherits and then allows to score are charged to the previous pitcher. That is why analysts also look at strikeouts, walks and WHIP, which measures how many runners a pitcher allows per inning regardless of whether they score.
The ratings above are informal benchmarks for major league play; youth, high school and college leagues have very different typical ERAs.
Frequently asked questions
How do you calculate ERA?
Multiply earned runs by 9, then divide by innings pitched. A pitcher who allows 20 earned runs in 60 innings has an ERA of 9 × 20 ÷ 60 = 3.00.
What does 6.1 innings pitched mean?
Six and one-third innings. The digit after the point counts outs, not tenths: .1 is one out (⅓ inning) and .2 is two outs (⅔ inning). The calculator converts 6.1 to 6.333 innings before dividing.
What is a good ERA?
In recent major league seasons the league-wide ERA has hovered between about 4.00 and 4.50. Below 3.00 is excellent, 3.00–3.99 is above average, and above 5.00 is poor for a regular starter.
What is the difference between earned and unearned runs?
An earned run scores without help from an error or passed ball. If a run would not have scored without the defensive mistake, the official scorer rules it unearned, and it does not count toward ERA.
How do I calculate ERA for high school or softball?
Use 7 instead of 9, because those games are seven innings long. Choose the 7-inning option and the formula becomes 7 × earned runs ÷ innings pitched.