A softball pitcher’s earned run average (ERA) is calculated as earned runs multiplied by 7, divided by innings pitched, because a regulation softball game is seven innings long. For example, a pitcher who allows 10 earned runs in 35 innings has an ERA of 2.00, meaning they allow an average of two earned runs per seven innings. The only tricky parts are deciding which runs count as earned and recording partial innings correctly, since innings are counted in thirds. This guide explains the formula, walks through examples, covers earned versus unearned runs, shows how to handle partial innings and explains how ERA compares with other pitching statistics.
Rulebook note: Official scoring rules, including how earned runs are determined, come from governing bodies such as NCAA, NFHS and USA Softball. Some leagues calculate ERA using a different game length, such as six innings for certain age groups. Check the scoring rules used in your league.
The ERA formula
ERA = (Earned runs x 7) / Innings pitched
The number 7 represents the number of innings in a regulation game. Multiplying by 7 converts the pitcher’s earned runs per inning into earned runs per full game, which makes ERAs easy to compare across pitchers who have thrown different numbers of innings. In baseball, the same formula uses 9 instead of 7 because baseball games are nine innings long.
ERA examples
| Earned runs and innings | Calculation | ERA |
|---|---|---|
| 10 ER in 35 IP | (10 x 7) / 35 | 2.00 |
| 6 ER in 21 IP | (6 x 7) / 21 | 2.00 |
| 15 ER in 42 IP | (15 x 7) / 42 | 2.50 |
| 4 ER in 20.1 IP (20 1/3) | (4 x 7) / 20.333 | 1.38 |
| 9 ER in 14.2 IP (14 2/3) | (9 x 7) / 14.667 | 4.30 |
Step-by-step: calculating ERA
- Count the earned runs the pitcher allowed.
- Count the innings pitched, including partial innings in thirds.
- Convert partial innings to decimals: one-third is about 0.333 and two-thirds about 0.667.
- Multiply earned runs by 7.
- Divide by innings pitched.
- Round to two decimal places.
Recording partial innings
Innings pitched are recorded in thirds, since each out is one-third of an inning. In box scores, 20.1 means 20 and one-third innings, and 20.2 means 20 and two-thirds innings. When calculating ERA, convert these to decimals: 20.1 becomes 20.333 and 20.2 becomes 20.667. Using 20.1 as if it were 20.1 in normal decimal form would produce a slightly wrong ERA. For example, a pitcher who records two outs in the eighth inning of a game after pitching seven full innings has pitched 7.2 innings, or 7.667 innings in decimal form.
What counts as earned
An earned run is a run that scores without the help of a defensive error or a passed ball. Runs that score because of hits, walks, hit batters, stolen bases, sacrifices and wild pitches are generally earned, since they are considered the pitcher’s responsibility. Runs that score because of a fielding error, a passed ball or catcher’s interference, or that would not have scored without such a mistake, are generally unearned.
Scorers determine earned runs by reconstructing the inning without the errors. If a runner reached base because of an error, any run they score is unearned. If an error extended the inning when there should have been a third out, runs scored after that point are unearned. Runs that would have scored even without the error remain earned.
Worked example: reconstructing an inning
Consider this inning. The first batter strikes out for one out. The second batter hits a routine ground ball, but the shortstop makes an error, so the batter reaches first. The third batter hits a home run, scoring two runs. The fourth batter flies out for the second out. The fifth batter singles, and the sixth batter doubles, scoring the fifth batter. The seventh batter grounds out to end the inning. Three runs scored in total.
To find the earned runs, replay the inning as if the shortstop had made the play. The second batter would have been out, making two outs. The third batter’s home run would still score one run, the batter himself or herself. The fourth batter’s fly out would then have been the third out, ending the inning. So only one run, the home run hitter’s, is earned. The run scored by the batter who reached on the error is unearned, and the run scored by the fifth batter is also unearned, because it came after the point where the inning should have ended. The pitcher is charged with three runs but only one earned run.
Why ERA is useful
ERA gives coaches, players and fans a simple way to compare pitchers who have thrown different numbers of innings. By removing runs caused by defensive mistakes, it tries to isolate the pitcher’s own performance. It is especially useful over a full season, when small samples even out. Over just a few innings, a single bad outing can inflate a pitcher’s ERA dramatically, so it is wise to be cautious when reading ERAs from early in the season or from pitchers with limited innings.
Relievers and inherited runners
When a relief pitcher enters with runners on base, those runners are charged to the pitcher who allowed them to reach base. If they score, the runs count against the original pitcher’s ERA, even though the reliever was pitching when they crossed the plate. This rule keeps each pitcher responsible for the runners they put on base.
ERA compared with other stats
| Statistic | What it measures |
|---|---|
| ERA | Earned runs allowed per seven innings |
| WHIP | Walks plus hits allowed per inning pitched |
| Strikeouts per seven innings | How often the pitcher strikes out batters |
| Walks per seven innings | Control and command |
| Opponent batting average | How often opponents get hits |
ERA is the most widely used pitching statistic, but it depends partly on the defense and on scoring decisions. Looking at several statistics together gives a more complete picture of a pitcher’s performance.
What makes a good ERA?
A good ERA depends on the level of play, the league and the era. In many competitive fastpitch leagues, an ERA under 2.00 is considered very strong, while top college pitchers often post much lower figures. In youth and recreational leagues, ERAs are often higher because of more errors, walks and variation in skill. Comparing ERAs within the same league or level is more meaningful than comparing across levels.
Common mistakes
- Using 9 instead of 7 in the formula.
- Treating 20.1 innings as a normal decimal instead of 20 and one-third.
- Counting unearned runs in the ERA.
- Charging inherited runners to the reliever.
- Not checking the league’s game length for the multiplier.
- Comparing ERAs across different levels without context.
Frequently asked questions
Why is softball ERA multiplied by 7?
Because a regulation softball game is seven innings, so ERA shows earned runs per full game.
What does 20.1 innings pitched mean?
Twenty and one-third innings, since each out is one-third of an inning.
Do runs scored on errors count toward ERA?
No. Runs that score because of errors or passed balls are generally unearned and do not count toward ERA.
