How to Use ERA Calculator
Enter Earned Runs Scored
Enter Innings Pitched
Enter the amount of innings in the game, typically 9 although little league may have 6-7
How to calculate Earned Run Average
There are 3 things needed to calculate ERA:
Earned Run Average Formula
- Earned Runs
- The number of runs that are enabled in an inning due to the pitcher, without error or passed balls from the defensive team on field.
- During a pitching switch, the original pitcher is still held accountable for the number of earned runs equal to the number of batters that he put on base. This is also applicable for any batters that replace a previous runner based on fielder’s choice, and is charged towards the original pitcher.
- There are occasions where earned runs may be charged against the individual pitcher, relief or otherwise, but unearned against the team if the run is scored on what would have been after three outs. Therefore a team’s ERA is generally lower than an individual pitcher’s ERA.
- Innings pitched
- The total number of innings the pitcher threw, measured by the number of batters and baserunners that are on mound due to the pitcher. A good player’s average IP may be fewer than 15 pitches per innings, averaging at 20 minutes per innings in MLB.
- Total number of innings in the game
- A game is typically composed of 9 innings. Three outs made is equal to one inning pitched. Extra innings are permitted in the case that both teams score a tie in number of runs made.
:( earned runs / innings pitched) X (number of innings in the game)
- Our pitcher plays 7 innings out of 9.
- Batter A singles. Batter A reaches second base by a passed ball while Batter B is on bat. Batter B then hits a home run. Batter C singles. Batter D grounds out, with Batter C advancing to second. Batter E doubles and puts Batter C home with Batter D on third. Batter F grounds Batter D to home and moves Batter E to third. Batter F singles Batter E home. Batter G grounds Batter F to second. Batter I strikes out to end the inning.
- Total scored runs are 5 ( A, B, C, D, E)
- We then divide earned runs by innings pitched: 5/7 = 0.71
- Now we multiply the result by the number of innings in the game which was 9: 0.71 X 9 = 6.39
- ERA is 6.39
- Incorporating the occasion where the scorer has to “reconstruct” the inning due to an error or passed ball from the defensive fielding team, they will determine the earned runs barring the runs enabled by the defensive error/passed ball.
- Batter A singles. Batter B triples Batter A home. Batter C grounds a fielder’s choice, with Batter B out. Batter D moves to second based on a two base error and Batter C advances to third. Batter E singles Batter C home and Batter D moves to third. Batter F grounds out and Batter D scoring and Batter E to second. Batter G doubles, scoring Batter E and moving Batter F to second. Batter I singles Batter F to third and scores Batter G.
- Total scored runs are 5 (A, C, D, E, G). In the reconstructed scoring, Batter A scores 1, Batter B is out, Batter C scores 1. Batter D is unearned due to the run by error. Batter E scores 1, and Batter G is unearned for being scored after three outs. Total earned runs now total 3.
- Divide the earned runs by the innings pitched: 3/7 = 0.42
- Multiply the result by the total innings in the game: 0.42 x 9 = 3.78
- ERA is 3.78
Earned Run Average is the number of earned runs a pitcher allows per inning. An earned run is determined by the scorer and counted as earned so long as no error or passed balls occur from the defensive team. Unearned runs are not included in ERA calculations.
Two rules of thumbs are used to determine an earned and unearned run. A run is never earned from a runner who reached based due to an error per above, nor is a run earned should the score occur after the third out.
ERA was originally made to account for a team’s offensive measurements in its batting success, but is nowadays used to evaluate pitchers based on how many runs they enable due to their pitching. ERA determines the success of a pitcher by calculating the average number of scored runs the pitcher allows without fault in the fielding team in any given game. Today an ERA below 4.00 is considered good.
It is important to note that comparing historical records for ERA does not have meaning as baseball has changed throughout its history. As before the 19th century, pitchers had extremely low ERAs but the pitcher's mound was much closer to the batter.
ERA can fluctuate depending on a pitchers place in the rotation, pitchers defense and the division. Relief pitchers generally have lower ERA than starting pitchers as they enter the play during a critical time. Such is the case when two outs are counted by the defensive team and there are 3 runners on base.
A Pitchers ERA can affect the teams winning percentage, you can calculate a teams winning percentage with our Winning Percentage Calculator.