ERA Calculator
Enter the number of earned runs allowed and innings pitched to calculate a pitcher's Earned Run Average. The result includes the ERA quality band (elite through poor), an ERA+ index showing performance versus the league average, and a worked step-by-step breakdown. You can adjust the innings-per-game setting for softball (7) or Little League (6), and the calculator handles baseball's fractional innings notation, where 6.1 means 6 innings and 1 out.
What is Earned Run Average (ERA)?
Earned Run Average is the most widely used statistic for measuring a pitcher's effectiveness. It represents the number of earned runs a pitcher would allow over a complete game if they maintained their current rate. "Earned" runs are those caused by pitching, not defensive errors or passed balls. A run that scores only because a fielder misplayed a routine grounder does not count against the pitcher's ERA, since the mistake was outside their control. The formula is: ERA = (earned runs allowed / innings pitched) x 9. The result is stated "per nine innings" because a standard MLB game is nine innings, giving ERA a natural scale across all outings regardless of length.
How to enter innings pitched - the scorecard notation
Baseball uses a unique shorthand for partial innings. Because each inning has three outs, a pitcher who finishes two full innings and records one additional out is listed as having pitched "2.1" innings on a scorecard. That does not mean 2.1 as a decimal fraction - it means 2 + 1/3, or 2.333. Similarly, "6.2" means 6 full innings plus 2 outs, equal to 6.667 decimal innings. This calculator automatically converts scorecard notation: any fractional digit of .1 is treated as one out (1/3 of an inning) and .2 is treated as two outs (2/3). If you want to enter a true decimal such as 6.333, you can do that too and the calculator will use it as-is.
ERA+ - comparing ERA across eras and parks
Raw ERA can be misleading because run-scoring environments vary enormously across leagues, seasons, and ballparks. ERA+ fixes this by adjusting the pitcher's ERA to a neutral league/park context and then expressing the result on a scale where 100 is exactly average. An ERA+ of 130 means the pitcher was 30% better than the league average; an ERA+ of 80 means 20% worse. This makes comparing pitchers across different eras much more meaningful: a 3.50 ERA in a high-offense season might represent better pitching than a 2.80 ERA in a dead-ball season. To use ERA+ in this calculator, enter the league ERA for the relevant season (the input defaults to 4.00, a reasonable modern MLB approximation).
ERA in different sports and league formats
Although ERA originated in baseball, the concept applies to any sport using a pitching/bowling role where the game has a defined inning count. Softball typically plays seven innings, so its ERA is calculated per seven innings rather than nine - a pitcher with the same rate of earned runs will have a lower ERA number in softball simply because the denominator is smaller. Little League and youth baseball often use five or six innings. This calculator lets you switch the "innings per game" setting so the output stays meaningful within whatever format you are tracking.
ERA quality scale (modern MLB context)
| ERA Range | Rating | Context |
|---|---|---|
| Under 2.00 | Elite | Historically exceptional - Cy Young-level season |
| 2.00-2.99 | Excellent | Top-tier ace; a clear asset for any rotation |
| 3.00-3.99 | Above average | Solid starter; better than most opponents |
| 4.00-4.99 | Average | League-typical; serviceable rotation piece |
| 5.00-5.99 | Below average | Struggling; gives up more runs than average |
| 6.00+ | Poor | Rotation liability; likely to face demotion |
Generally accepted ERA quality bands for starting pitchers in professional baseball. Thresholds shift slightly across eras and leagues.
Frequently asked questions
What is a good ERA in baseball?
In modern MLB, an ERA under 3.00 is considered excellent and marks an ace-caliber starter. An ERA between 3.00 and 4.00 is above average and still highly desirable. Around 4.00 to 4.50 is roughly league average. Above 5.00 is below average, and above 6.00 typically puts a pitcher's roster spot at risk. These thresholds shift somewhat by era - in the 1960s pitcher's era, sub-2.00 ERAs were far more common than they are today.
What counts as an earned run vs. an unearned run?
A run is unearned if it scores because of a defensive error, a passed ball, or because an out was not recorded that should have been. The official scorer reconstructs the inning as if the error never happened; any run that would not have scored in that hypothetical inning is unearned. Unearned runs are tracked in a pitcher's stats but do not count toward ERA, because the pitcher is not responsible for defensive mistakes.
Why does baseball use innings pitched as a decimal like 6.2?
Baseball scorecard notation records partial innings as the number of outs beyond full innings, not as a decimal fraction. Because each inning has three outs, 6.1 means 6 full innings plus one out, which is 6.333 real innings, and 6.2 means 6 full innings plus two outs, or 6.667 innings. You cannot have a fractional digit of .3 or higher in standard notation - that would be a full additional inning. This calculator converts .1 and .2 automatically.
What is ERA+ and how does it differ from ERA?
ERA+ adjusts a pitcher's ERA for the run-scoring environment (league offensive level and home ballpark) and then rescales so that 100 equals exactly the league average. A higher ERA+ is always better: 150 means 50% better than average, 80 means 20% worse. ERA+ makes cross-era comparisons far more valid, since a 3.50 ERA meant something very different in 1968 than in 2019.
Can ERA apply to relief pitchers and closers?
Yes, ERA is calculated the same way for relievers and closers, but the interpretation differs. Relievers pitch fewer innings so ERA is based on smaller samples, making it more volatile game-to-game. A closer with a 2.50 ERA across 60-70 innings is considered excellent. Context also matters: a reliever who inherits runners is not charged for those runners if they score, but the runs count against the reliever who actually allowed the hit or walk that let them in.
Who holds the career and single-season ERA records?
The all-time career ERA record belongs to Ed Walsh at 1.82, though he pitched in the dead-ball era when run-scoring was extremely low. Among pitchers with at least 1,000 innings, Addie Joss (1.89) and Three Finger Brown (2.06) are close behind. The most famous modern single-season ERA is Bob Gibson's 1.12 in 1968, a performance so dominant it prompted MLB to lower the pitching mound the following year. Dutch Leonard holds the single-season record at 0.96 in 1914, over 224.2 innings.
How many innings pitched does ERA need to be meaningful?
Statisticians generally consider roughly one inning per game played (about 30 innings for a 30-game sample) a minimum for ERA to stabilize into a reliable indicator. In a full MLB season, starting pitchers log 150-200 innings, giving a highly reliable sample. For a relief pitcher or someone with only 10-15 innings, a single bad outing can swing ERA dramatically, so small-sample ERAs should be treated with caution.