To compute a baseball pitcher’s earned run average (ERA), divide the number of earned runs he has allowed by the number of innings he has pitched, and multiply by nine.
For example, last year pitcher John Smith pitched 180 innings and allowed 90 runs. The ERA is calculated:
90 runs divided by 180 innings = 0.5 times 9 = 4.50
The reason the first number is multiplied is to make the numbers comparable to a full baseball game, which is nine innings. Without the multiplication, the number would show as 0.5, which would be a very low number historically. One of the lowest ERAs ever was the 1.12 figure for Bob Gibson in 1968.
ERAs can be calculated for a season or for each game, although the more games used, the useful the number. Team ERA can also be calculated in the same manner as individual pitchers.
How Earned Runs are Determined
For Major League Baseball games, and many other organized games in the Minor Leagues and College Baseball, an official scorer is designated to score the game, that is, to determine, among other things, when a player reaches base, whether it related to a hit or an error.
If the scorer determines that there is an error, and if a run scores in the inning, he or she must determine whether the run would have scored without the error. If that is not the case, if the run is considered to be unearned.
If the run would have scored without the error, it is deemed earned, and counted towards earned runs in calculating the earned run average. If a player makes an error on what would have been the third out, then all runs scored after would be considered unearned. Along with errors, passed balls may also result in a run being declared unearned.
The Importance of ERA in Fantasy Baseball
Earned Run Average is a more important statistic than won-loss percentage when selecting a player for a Fantasy League, or Rotisserie League team. Wins and losses are very dependent on the quality of the fielding and hitting of the other players on the team.
Depending on the type of league, opponents’ batting average or number of strikeouts may be important if those statistics directly impact the scoring of the league. ERA is a valuable overall stat that enables a manager to quickly determine the quality of the pitcher.
Once a manager has pre-qualified a group of pitchers based on ERA, they can then review the other important stats that the fantasy league uses for scoring.
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