How to Calculate ERA
ERA = (9 × Earned Runs) ÷ Innings Pitched
To calculate Earned Run Average, you multiply the total number of earned runs allowed by 9 (the standard number of innings in a baseball game) and then divide that result by the total number of innings pitched.
Calculation Steps:
- Find the total Earned Runs (ER) allowed by the pitcher.
- Determine the total Innings Pitched (IP). Remember: 1 out = 1/3 inning (0.33), 2 outs = 2/3 inning (0.67).
- Multiply ER by 9.
- Divide that total by the IP to get the ERA.
What counts as an earned run?
An earned run is any run that scores as a direct result of base hits, sacrifice flies, walks, or stolen bases, provided the inning hasn't been prolonged by errors or passed balls. The official scorer determines whether a run is earned or unearned by reconstructing the inning without the fielding mistakes.
How Innings Pitched works
In baseball statistics, innings pitched are often written with a decimal-like notation (e.g., 6.1 or 6.2). However, this is not a true decimal. 6.1 means 6 innings and 1 out (6.333 innings), while 6.2 means 6 innings and 2 outs (6.666 innings). Our calculator handles this conversion automatically.
Examples
Example 1: The Quality Start
A pitcher allows 2 earned runs over 7 innings.
(9 × 2) ÷ 7 = 18 ÷ 7 = 2.57 ERA
Example 2: Relief Appearance
A reliever allows 1 earned run and records 2 outs (0.667 innings).
(9 × 1) ÷ 0.667 = 9 ÷ 0.667 = 13.50 ERA
Frequently Asked Questions
What is ERA in baseball?
ERA stands for Earned Run Average. It represents the average number of earned runs a pitcher would give up over a nine-inning game.
How do I calculate ERA?
The formula is (9 × Earned Runs) / Innings Pitched. For example, if a pitcher allows 3 earned runs in 6 innings, their ERA is (9 × 3) / 6 = 4.50.
What is a good ERA?
In modern MLB, an ERA under 4.00 is considered solid, while an ERA under 3.00 is elite. However, 'good' can vary by era and league scoring environment.
What’s the difference between earned and unearned runs?
Earned runs are allowed through hits and walks. Unearned runs occur due to fielding errors or passed balls that prolonged an inning or allowed a base runner to score who otherwise wouldn't have.
How do outs convert to innings pitched?
In baseball stats, each out is one-third (1/3) of an inning. So, 6 innings and 1 out is recorded as 6.1 or 6.333, and 6 innings and 2 outs is 6.2 or 6.667.
Can ERA be infinite?
Yes. If a pitcher allows one or more earned runs without recording a single out, their ERA is mathematically infinite because you cannot divide by zero innings.
Does ERA apply to softball the same way?
Fastpitch softball typically uses a 7-inning calculation (7 × ER / IP) because regulation games are 7 innings long, though the ERA Calculator can be used for both by adjusting the multiplier contextually.
Why is ERA multiplied by 9?
The multiplier represents the number of innings in a standard regulation baseball game, providing a normalized per-game average for pitchers.