How to Calculate an Earned Run Average

With the exception of wins and losses, earned run average (ERA) is the most important baseball statistic for pitchers. ERA says how many earned runs a pitcher gives up per nine innings pitched.

Difficulty: Easy

Instructions

1. Add up the total innings pitched. For every out that is recorded while you are pitching, you get one-third of an inning.

2. Add up the total number of earned runs given up. If there are no errors in the inning, all the runs are earned runs. If there are errors, reconstruct the inning without the errors to see how many runs would have scored if the fielding had been perfect.

3. Multiply the earned runs by 9.

4. Divide by the total innings pitched.

5. Round the number to the second decimal place. For example, 3.2051 is 3.21.

Tips & Warnings

• When calculating earned runs, always give the benefit of the doubt to the pitcher.
• If an error occurs with two outs, all runs scored after that error are unearned runs.
• Any runner who scores is the responsibility of the pitcher who let him or her get on base, even if that pitcher has left the game when the runner scores.
• If you leave the game while a batter is still at bat and the pitching count is in the batter's favor (that is, there are more balls than strikes in the count), then the batter is your responsibility.

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