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How to Calculate ERA in Baseball

Learn how to calculate ERA -- and see if your favorite pitcher is really as strong as he seems -- with this Howcast video.


  • Step 1: Calculate number of innings pitched Determine the total number of innings pitched. For partially played innings, add in one-third of an inning for each out recorded. For example, if a pitcher threw 6 full innings, then recorded one out in the seventh, he threw 6 1/3 innings.
  • Step 2: Calculate earned runs allowed Calculate the total number of earned runs allowed. For innings where no errors occurred, this will be the total number of runs. If errors did occur, add in only the runs that would have scored had there not been an error.
  • TIP: Remember to include earned runs that might come after the pitcher leaves the game. If a hitter gets on base against a pitcher, that runner is his responsibility, even if the pitcher has been taken out of the game.
  • Step 3: Divide earned runs by innings pitched Divide the total number of earned runs by the total number of innings pitched.
  • Step 4: Multiply by 9 to find ERA Multiply by 9, and round this number to 2 decimal places to find the pitcher's ERA. For Major League ball players, an ERA of 4 is about average, and an ERA of 2 or less is excellent.
  • FACT: Ed Walsh, who played with the Chicago White Sox from 1904 to 1916, has the lowest career ERA in Major League baseball at 1.82. But the statistic is unofficial, since the American League didn't accept ERA as a statistic until 1913.

You Will Need

  • Calculator
  • Basic understanding of baseball

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