What is ERA in Baseball? Everything You Need To Know


What is ERA in Baseball?

Numerous statistics are used to evaluate a hitter’s effectiveness, such as batting average, slugging percentage, and OPS, to name a few. Essential statistics are also used to measure a pitcher’s production. One of the most important is ERA. So what is ERA in baseball, and how do you calculate it?

Let’s take a look at those questions and more.

What Does ERA Stand for in Baseball?

Henry Chadwick, a 19th-century English-American statistician, and sportswriter, invented the statistic ERA, which stands for “earned run average.” Chadwick was key to other things still used today to evaluate baseballs, such as the batting average and box score.

How Does ERA Work?

The main goal of a pitcher is to prevent the other team from scoring a run. A pitcher’s earned run average indicates how many earned runs they allow over a nine-inning game. But what is an earned run versus an unearned run?

An earned run results from the outcome of a pitch as opposed to one that scores due to an error from a player on the field. An unearned run is caused directly by a throwing error or other botched ball in the field where the official scorer rules an error.

The ERA is quite basic yet is a good indicator of how well a pitcher performs overall throughout a season. The career ERA gives a good indication of how effective a pitcher has been over a long period of time.

What is the Formula to Calculate ERA?

The calculation for earned run average is quite basic. Simply take the number of earned runs allowed multiplied by nine and divide the total by the number of innings pitched. ERA values are rounded to two decimal places and give the average number of earned runs allowed by a pitcher over nine innings.

Let’s take an example. Suppose a starting pitcher through 200 innings throughout a season and allowed 75 runs, of which 67 were earned runs. Using the formula for ERA, take 67 multiplied by nine and divide that total by 200. This comes out to an ERA of 3.02, which would be an excellent season for this starting pitcher.

What Happens if The Pitcher Leaves the Game with Men on Base?

Suppose a pitcher leaves a game with runners on base, any runner that he allowed to get on base that scores counts as his earned run. The exception is if those runners score as a result of an error. Therefore, the starting pitcher is rooting extra hard for the relief pitcher to bail him out of the inning.

Is a High or Low ERA Better?

Since the primary purpose of a pitcher is to prevent the opposing team from putting runs on the board, a low ERA is better. The lower the ERA, the fewer earned runs per nine innings, on average, that cross the plate. Therefore, the lower the ERA, the better.

What is considered a good earned run average in today’s game differs from that of some past eras that were pitching-dominated or the “dead ball era.” In today’s game, an ERA for a starting pitcher below 3.00 is very good, and an ERA below 2.00 is exceptional. An earned run average in the low to mid 4s is about average, and anything over 5.00 is poor.

Who Had Some Great ERAs in their Career?

The lowest career earned run average came from a pitcher who competed in MLB over a century ago. Ed Walsh took the mound from 1906 through 1914 and posted a career earned run average of 1.79.   

Bob Gibson of the St. Louis Cardinals was a starting pitcher’s lowest ERA for a season. He dominated opponents that season and had an ERA of a minuscule 1.12. For his career, the Hall of Famer had an earned run average of 2.91.

Although known for his tremendous power at the plate, Babe Ruth was an excellent pitcher with the Red Sox and had a career ERA of 2.28. 

A more modern pitcher with an excellent career era was Pedro Martinez. He retired in 2009 with an earned run average of 2.93 with a career-best 1.74 in 2000.

As for relief pitching standards, look no further than Mariano Rivera, who had 11 seasons with an ERA under 2.00 and a career ERA of 2.21. No wonder he is the only player to ever receive 100 percent of the votes for the Hall of Fame.

What Pitcher Has the Lowest ERA Ever?

You must go back to the earliest days of league history to find the lowest single-season earned run average. Tim Keefe of the Troy Trojans allowed only 10 earned runs over 105 innings in 12 starts for an ERA of 0.86. Keefe’s won-loss record was 6-6, despite a record-setting earned run average.

Dutch Leonard had an earned run average of 0.94 while pitching for the Boston Red Sox in 1914. His season was even more remarkable than Keefe’s since Leonard pitched 224 innings and allowed only 24 runs while posting a record of 19-5.

How is ERA Different for a Starter Versus a Reliever?

The biggest difference between a starting pitcher and a relief pitcher is the number of innings pitched per game. Since a relief pitcher will go only through an inning or maybe two innings, he can go full force on every pitch.

A starting pitcher is expected to go at least six innings, so he may try to get batters out with fewer pitches instead of trying to strike out more. A starting pitcher can have a very bad game and make up for it with a couple of good starts.

However, suppose a relief pitcher has five great outings, not allowing a run but giving up four in one inning in his next game. His earned run average will skyrocket, but in all reality, the number is a little deceptive since he pitched well in most of his appearances. It will also take much longer for a reliever to lower his earned run average after a bad game. 

Can You Have a Zero ERA?

A zero earned run average means the pitcher hasn’t given up any earned runs. While this happens during games, it doesn’t happen during a season, although technically, it is possible.

This should not be confused with an undefined ERA, also known as infinite earned run average. This occurs when a pitcher allows earned runs without getting any batters out. The calculation involves a division by zero, which is undefined.

Simple Ways Pitchers Can Improve Their ERA

Throwing More Strikes: A higher percentage of strikes thrown will lead to more outs and fewer runs scored against the pitcher. 

Inducing More Weak Contact: This can be done by pitching to spots where hitters are less likely to make solid contact or by throwing pitches that are difficult to hit hard. 

Limiting The Damage In Big Innings: Avoid giving up extra-base hits and walks in clusters, which can lead to a high number of runs being scored in a single inning.

Conclusion: What Is ERA In Baseball?

The earned run average is a very effective way to evaluate the performance of both a starting pitcher and a relief pitcher. It is the average number of earned runs allowed throughout nine innings. This is a better indicator of performance than a win-loss record.

Nolan Ryan once had a record of 8-16, but his ERA was under 3.00. Just looking at the record, it says he had a bad season, but his low ERA said otherwise. On the other hand, Jamie Moyer once had a record of 13 wins and ten losses, but his earned run average was a very high 5.49. Who was more effective?

It was Nolan Ryan. An ERA is an excellent indicator of overall pitcher effectiveness.