How to Calculate ERA (Earned Run Average)
Earned Run Average (ERA) is one of the most vital statistics in baseball and softball for evaluating a pitcher's effectiveness. It calculates the average number of earned runs a pitcher would give up if they were to pitch an entire, standard-length game.
- Earned Runs = Runs scored by the opposing team that are the pitcher's fault (excludes runs resulting from fielding errors or passed balls).
- Innings Pitched = The total number of innings the pitcher completed.
- 9 = The number of innings in a standard professional baseball game. (Use 7 for high school or softball, and 6 for Little League).
Note: When dealing with fractional innings, 1 out equals 0.333 of an inning, and 2 outs equal 0.667 of an inning.
A lower ERA is always better. It indicates that the pitcher allows fewer runs to score. For professional starting pitchers, an ERA under 3.00 is considered excellent, while an ERA around 4.00 is generally considered average.
| ERA Range | Evaluation | Description |
|---|---|---|
| Under 2.50 | Elite / Cy Young Caliber | Exceptional performance; rarely allows runs. |
| 2.50 - 3.50 | Great / All-Star | Top-tier starting pitcher or strong reliever. |
| 3.50 - 4.50 | Average / Solid | Reliable, everyday starting pitcher. |
| 4.50 - 5.50 | Below Average | Struggling starter or backend rotation pitcher. |
| Over 5.50 | Poor | Vulnerable to giving up multiple runs per game. |
Frequently Asked Questions (FAQ)
What counts as an "Earned" Run?
An earned run is any run that scores against a pitcher without the benefit of a fielding error or a passed ball. If a batter gets a hit, steals a base, and is driven in by another hit, that run is "earned" by the pitcher. If a batter reaches base purely because the shortstop dropped a routine pop-up and later scores, that run is "unearned" and does not affect the pitcher's ERA.
How do I enter partial innings?
Because there are 3 outs in a half-inning, each out represents one-third of an inning. If a pitcher pitches 5 full innings and gets 1 out in the 6th, their Innings Pitched (IP) is 5.33. If they get 2 outs, it's 5.67. If they pitch exactly 5 innings, enter 5 or 5.0.
Why do we multiply by 9?
Multiplying the runs-per-inning ratio by 9 normalizes the statistic to a standard nine-inning baseball game. It answers the question: "If this pitcher pitched an entire 9-inning game at their current pace, how many runs would they give up?" For leagues that play 7-inning games, you multiply by 7 instead.