Earned run average
In baseball, earned run average (abbreviated to ERA) is the mean of earned runs given up by a pitcher. It is measured per nine innings pitched in Major League Baseball. ERA is found by dividing the number of earned runs allowed by the number of innings pitched and multiplying by nine. For example, if a pitcher allowed 25 runs during 95 innings pitched, his ERA would be 25 / 95 x 9, or 2.37.