Calculate Earned Run Average (ERA) from earned runs and innings pitched. Enter baseball-style innings notation like 6.1 (6⅓ innings) or 6.2 (6⅔ innings) directly.
| ERA Range | Rating |
|---|---|
| ~ 2.99 | Ace-level (sub-3.00) |
| 3.00 - 3.74 | Excellent |
| 3.75 - 4.49 | Average |
| 4.50 - 5.24 | Below Average |
| 5.25 + | Poor |
Earned Run Average (ERA) measures how many earned runs a pitcher allows on average per 9 innings. The formula is 'earned runs × 9 ÷ innings pitched', and since both KBO and MLB games run 9 innings, the same formula applies. For example, allowing 30 earned runs over 90 innings gives an ERA of 3.00. A lower ERA indicates a better pitcher.
Because an inning ends after 3 outs, 6.1 innings means 6 innings plus 1 out (1/3 inning), and 6.2 innings means 6 innings plus 2 outs (2/3 inning). Treating 6.1 as a literal decimal (6 and 1/10) understates the true innings pitched and produces an artificially low ERA. This calculator's baseball-notation toggle automatically converts .1 and .2 into 1/3 and 2/3 innings for an accurate ERA.
For starting pitchers, an ERA in the 2s (below 3.00) is typically considered ace-level, 3.00-3.74 excellent, 3.75-4.49 average, 4.50-5.24 below average, and 5.25+ poor. In the KBO league, a season ERA in the low 3s is generally regarded as top-tier starter performance.
ERA can be influenced by fielding errors and luck (BABIP), so it doesn't fully isolate a pitcher's true skill. FIP (Fielding Independent Pitching) addresses this by estimating ERA using only outcomes a pitcher directly controls — home runs, walks, and strikeouts. Viewing ERA alongside WHIP (walks plus hits per inning pitched) gives a more accurate picture of a pitcher's actual run-prevention ability.
To lower ERA, first reduce walks to minimize baserunners, and build command to attack the strike zone consistently. Mixing pitch types and changing speeds helps disrupt hitters' timing. Getting ahead in counts to increase strikeout rate reduces balls in play and thus scoring risk. Strengthening the lower body and core helps maintain stuff quality deep into starts, making ERA easier to sustain in later innings.