ERA in baseballs stands for “earned run average.” It is used to measure a pitcher’s performance and was originally created during the 1900s to rate the effectiveness of relief pitchers. Today, it is one of most widely recognized statistics used to assess a pitcher’s ability.
An ERA measures the average number of runs given up by a pitcher over the course of a nine-inning game. It does not include runs resulting from mistakes made by other players in the field. The ERA was created out of the necessity to determine each pitcher’s effectiveness during games where relief pitchers help share the load.
An ERA is calculated by adding up the earned runs and dividing the number by the number of innings pitched. That number is then multiplied by 9. For example, if a pitcher allowed 25 earned runs over 100 innings, you would divide 25 by 100 and then multiply by 9. The ERA would be 2.25.
The lower the ERA, the better the pitcher is considered. During the 1900s, some pitchers had ERAs under 2.00. However, as the rules of the game have evolved over the years, an ERA under 4.00 is now considered somewhat effective, while an ERA under 2.00 is rare. An ERA above 6.00 usually is considered unacceptable.
Some critics don’t consider an ERA to accurately reflect a pitcher’s ability, or his potential for success. Although it accounts for the ability to get batters out and prevent runs, it leaves out a variety of external factors that may skew the results. According to ESPN, some of these factors may include bullpen support, team support and defense, unearned runs and home-field advantage.