Baseball ERA Calculator
Calculate a pitcher's Earned Run Average (ERA) from earned runs allowed and innings pitched. Essential for evaluating pitching performance and comparing pitchers across different workloads or seasons.
About this calculator
Earned Run Average (ERA) is the most fundamental pitching statistic in baseball. It represents the average number of earned runs a pitcher would allow over a complete 9-inning game. The formula is: ERA = (Earned Runs × 9) / Innings Pitched. Multiplying by 9 scales the result to a full game, allowing fair comparison between a starter who threw 200 innings and a reliever who threw 40. 'Earned runs' excludes runs that scored due to fielding errors, keeping the stat focused on the pitcher's own performance. In MLB, an ERA below 3.00 is considered excellent, 3.00–4.00 is above average, and above 5.00 is generally poor for a starting pitcher.
How to use
Suppose a starting pitcher has allowed 42 earned runs over 135.2 innings pitched this season. Convert the partial inning: 135.2 innings = 135 + 2/3 = 135.667 innings. Apply the formula: ERA = (42 × 9) / 135.667 = 378 / 135.667 = 2.79. That is an excellent ERA, ranking among the top starters in the league. Enter your earned runs and innings pitched values and the calculator handles the arithmetic instantly, including fractional innings.
Frequently asked questions
What does ERA mean in baseball and how is it calculated?
ERA stands for Earned Run Average, a statistic measuring how many earned runs a pitcher allows per 9 innings. It is calculated as ERA = (Earned Runs × 9) / Innings Pitched. The '×9' scales any number of innings to a full game equivalent. Only runs caused directly by the pitcher — not those resulting from fielding errors — count as earned runs, making ERA a pitcher-specific performance measure.
What is a good ERA for a starting pitcher in MLB?
Generally, an ERA below 3.00 is considered elite and often contends for a Cy Young Award. ERAs between 3.00 and 3.75 are very good for a front-line starter. The league-average ERA in MLB typically falls between 4.00 and 4.50 depending on the season and offensive environment. An ERA above 5.00 is usually unsustainable for a rotation starter and may indicate a move to the bullpen or a mechanical adjustment is needed.
Why are earned runs used instead of total runs when calculating ERA?
Using only earned runs isolates the pitcher's individual contribution from defensive mistakes made behind him. If a runner reaches base on a fielding error and later scores, that run is 'unearned' because the inning would theoretically have ended without the error. Including unearned runs would penalize pitchers for poor fielding they cannot control, making cross-team and cross-era comparisons less meaningful and unfair.