ERA calculator
Enter innings in baseball notation — 6.1 for six and a third, 6.2 for six and two-thirds.
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Baseball notation: .1 is one out, .2 is two outs.
How do you calculate ERA?
Multiply earned runs by nine, then divide by innings pitched. The catch is that baseball writes a third of an inning as .1 and two-thirds as .2, so 6.2 innings means 6.667, not 6.2. Treating it as an ordinary decimal is the single most common ERA error.
The notation trap
Innings pitched is recorded in thirds, because an inning ends after three outs. A pitcher who records one out beyond a complete inning has pitched one and a third innings, written 1.1.
That decimal point is not a decimal. It is a count of outs. A line of 6.2 innings means six innings plus two outs, which is 6.667 innings — and dividing by 6.2 instead produces an ERA that is roughly 7% too high.
The calculator converts the notation before dividing, and tells you when it has done so. If you would rather enter a true decimal, it accepts that too — anything other than .1 or .2 after the point is read literally.
The formula
Runs scaled to a full game, over true innings.
true innings = whole innings + (outs ÷ 3)6.1 → 6.333 6.2 → 6.667ERA = earned runs × 9 ÷ true inningsWHIP = (walks + hits) ÷ true inningsin a seven-inning league, replace the 9 with 7
Only earned runs count. A run that scores because of a fielding error is unearned and is excluded from ERA, which is the whole point of the statistic — it tries to isolate the pitcher from the defence behind them.
WHIP makes no such distinction and counts every walk and hit allowed regardless of what happened afterwards. The two together say more than either alone: a low ERA with a high WHIP usually means a pitcher who allows plenty of traffic but escapes trouble.
Worked example: 3 earned runs in 6.2 innings
A starter allows 3 earned runs over 6 innings and 2 outs, in a nine-inning league.
- Innings as written6.2
- True innings6.6667
- 3 × 927
- 27 ÷ 6.66674.05
An ERA of 4.05 for that outing.
Dividing by 6.2 instead gives 4.35, which is 0.30 higher. Across a season that error compounds into a materially different-looking pitcher.
Reading the number
- Below 2.00 — elite by any standard
- 2.00 to 3.00 — strong, comfortably above average for a starter
- 3.00 to 4.00 — around or better than typical major-league average
- 4.00 to 5.00 — below average for a starter, playable in relief
- Above 5.00 — the sort of figure that costs a rotation spot
These bands shift with the era and the league. Offensive environments change, and an ERA that was average in one decade can be well above or below average in another.
Common questions
What does 6.2 innings pitched mean?
Six innings plus two outs, which is six and two-thirds innings, or 6.667. The digit after the decimal point counts outs, not tenths. This is why an ERA calculator that treats it as a plain decimal returns a wrong answer.
What is a good ERA?
Under 3.00 is strong for a starting pitcher and under 2.00 is elite. Around 4.00 is roughly league average in most modern seasons. The bands move with the offensive environment of the era and league.
What is the difference between ERA and WHIP?
ERA measures earned runs allowed per nine innings and excludes runs caused by fielding errors. WHIP counts walks and hits allowed per inning regardless of outcome. A low ERA with a high WHIP suggests a pitcher who allows baserunners but escapes damage.
Why are unearned runs excluded?
Because ERA is trying to measure the pitcher rather than the defence. A run that scores only because of a fielding error is charged to the team but not to the pitcher's ERA. The official scorer decides which runs are earned.
Does ERA work for seven-inning games?
Not with the standard formula. ERA scales runs to a full game, so a seven-inning league needs the multiplier changed from nine to seven. The calculator has a field for this — leaving it at nine understates the ERA in a shorter format.
Where these numbers come from
- MLB — Earned Run Average (ERA) Official definition of ERA and the treatment of earned runs.
- MLB — Innings Pitched (IP) Confirms that thirds of an inning are recorded as .1 and .2.
Last verified 2026-08-01 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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