How to Calculate Earned Run Average

Earned run average is a key indicator of a pitchers effectiveness so correctly calculating this is important.

Difficulty: Moderate

Instructions

1. I love baseball and statistics so I used to do this for all my teams. I also kept batting statistics and other data but earned run average was the toughest to figure out.
   Earned run average measures how many runs a pitcher gives up per game. The calculation of this is fairly simple but determining what an earned run is versus an unearned run is a bit more complex.

2. To calculate earned run average determine the total number of innings pitched including partial innings such as 1/3 of an inning. Divide that by the number of innings in a game to get the number of games. Then divide the number of earned runs by the number of games. In baseball divide the number of innings by 9, but for softball it may be more accurate to divide the number of innings by however many innings constitute a softball game. I’ve played in softball leagues that play 7 innings. The formula for this would look like this;
   Innings/innings in a game = games
   Earned runs /games = ERA

3. For example this season a pitcher pitched 94 2/3 innings or 94.667. He has given up 45 earned runs. So 94.667/9 =10.518 games. Now divide the 45 runs by games or 45/10.518 =4.278 or 4.28 earned run average.
   Now if you play only 7 innings a game you might want to calculate that by dividing innings by 7 creating a unique softball ERA statistic.

4. The other important thing is determining an earned run. There are three instances where a run is unearned;
   Any run scored as a result of an error
   A runner advances on an error and scores on a play that would not have allowed the runner to score is unearned
   Any run scored after the third out would have been made

Tips & Warnings

• Any runners left on base when a reliever comes into the game are the responsibility of the previous pitcher. So if the starter left the game with the bases loaded and the reliever gives up a home run the starter is charged with three earned runs and the reliever with one. This is assuming the runners were not on base due to an error or that an error would have been the third out.
• In MLB it is up to the official scorer to determine a hit or an error but in softball the team manager or an umpire could make that determination.