What is ERA in baseball?

Written by Mark Bailey
Last updated on

ERA is a baseball acronym that stands for Earned Run Average. It is a metric that measures the number of earned runs a pitcher allows per nine innings pitched. According to MLB.com, “ERA is the most commonly accepted statistical tool for evaluating pitchers.”

How does ERA work?

A pitcher’s primary job on the mound is to limit runs, so ERA measures how well a given pitcher performs that job. To calculate ERA, you will need to know the number of innings pitched and the total number of earned runs allowed by that pitcher.

How do you calculate ERA?

Once those numbers are known, one can calculate ERA by dividing earned runs over innings pitched, then multiplying by 9 to project for an entire game (Earned runs/innings pitched x 9). ERA  is expressed as a whole number followed by two decimal places (I.e., Max Fried’s current career ERA is 3.40)

What are earned runs and unearned runs?

ERA is an individual statistic unique to pitchers, but there is no denying that it can be drastically affected by the team’s defense. ERA accounts for this by only including “Earned” runs and removing “Unearned” runs from the evaluation.

Earned runs are the pitcher’s fault or responsibility, assuming the support of competent play from the defense. These include runs scored by runners who remained on base, allowed by the said pitcher, following their exit from the game.

An unearned run is one that would not have scored without a committed error by the defense (including the pitcher) or a passed ball.

There are several nuanced scenarios where potential runs can change from earned to unearned and vice versa depending on what plays out while said runner is on the base paths. As an example:

A runner on first base advances to second on a passed ball, and the next batter walks. Since the runner would have been at second base anyway, the passed ball no longer affects the earned/unearned calculation. Conversely, a batter/runner may make his entire circuit around the bases without an error, but the run would be counted as unearned if an error prevented the third run from being made.

Is High ERA Good or Bad?

For pitchers, the lower the ERA, the better.  Unlike other statistics that accumulate to a point where the higher number is better, a high ERA is likely a good indicator of a poor pitcher.

A low ERA translates into fewer runs scored against that particular pitcher. Conversely, a high ERA typically indicates a pitcher not missing many bats or allowing too many walks. 

What is a good/bad ERA?

What constitutes a good vs. bad ERA can depend largely on the level of baseball under evaluation. Younger levels of baseball tend to have lower ERA’s as a result of shorter games and less overall depth of talent, generally speaking.

An ERA between 4.00 and 5.00 is considered average for a Major League Baseball player in today’s era. This number has changed over time and fluctuates when new rules are put into play that favor hitters or new ballpark dimensions are introduced. Below is an accepted rule of thumb for ERA evaluation (courtesy of fandom.com).

  • Exceptional 2.00 and under
  • Excellent 2.00 – 3.00
  • Above Average 3.00 – 4.00
  • Average 4.00 – 5.00
  • Below Average 5.00 – 6.00
  • Poor 6.00 and above

Why a low ERA is better than a high ERA

A lower ERA typically means that the opposing team will not score as many runs, thus allowing the pitcher’s team a better opportunity to win the game. Conversely, a high ERA indicates that the pitcher’s team may need to score an above-average number of runs to win the game.

How is ERA Different for a Starter vs. Reliever?

In an article by famed baseball writer and statistician Bill James, he explains that “A relief pitcher undoubtedly has an ERA advantage over a starting pitcher, created by the fact that he often begins his work with one or two men out in the inning.”

Another factor impacting this advantage for relievers is that relief pitchers are frequently required to produce far fewer outs than a starting pitcher, thus allowing fewer opportunities for scoring. Therefore, their success in one inning is extrapolated to 9 innings the same way as a starting pitcher’s performance, which occurs over 5-7 innings.


Who has the lowest ERA ever?

The record for lowest ERA in a season is 0.86, set by Tim Keefe in 1880. The modern record is 1.12, set by Bob Gibson in 1968. The lowest single-season ERA of an active pitcher is 1.66, achieved by Zack Greinke in 2015. The career record is 1.82, held by Ed Walsh. The active player with the lowest career ERA is Clayton Kershaw, with an ERA of 2.44 through the 2019 season.

What is a good ERA in Major League Baseball?

Any ERA below 4.00 is above average in Major League Baseball.

What is a good ERA in College/High School Baseball?

According to the baseball blog, 4busydads.com, when college scouts evaluate pitchers, the rough rule of thumb for ERA evaluation is as follows: 

  • 2.00 or less: Division I talent
  • 2.01 to 3.00: Division II talent
  • 2.50 to 3.5: Division III talent
  • Less than 4.00: Junior College talent

It is essential to note this is far from the only factor used to evaluate talent.

ERA’s in high school and college are generally lower than those in Major League Baseball due to the lack of depth of talent.

What is a good career ERA in baseball?

If you manage a career ERA of 3.30 or better, you would be in the top 300 pitchers of all time. Madison Bumgarner is currently #300 with a career ERA of 3.30.

Can you have a zero ERA?

If a pitcher does not allow any runs, they will have a 0.00 ERA.

What is the highest possible ERA?

If a pitcher enters a game and gives up one or more runs without recording a single out, their ERA will be listed as INF for Infinite until their next outing.

What happens if a pitcher leaves the game with men on base?

A pitcher leaving the game is “responsible” for the runners that remain on base, as far as ERA is concerned. Therefore, if the base runners come around to score, their runs will count towards the original pitcher’s ERA (assuming they were not on base due to an error, in which case the run would be unearned and not impact the ERA).

What are the drawbacks to ERA as a stat?

ERA has difficulty accounting for the difference between an average defense and an exceptional one. Thus, if an average pitcher has an outstanding defense behind him, his ERA may indicate that he is similarly talented to a “better” pitcher with a worse defense behind him.
ERA also tends to favor relief pitchers or pitchers who have shorter appearances.

In Summary

ERA is the most widely accepted statistic for evaluating pitchers, but it should not be the only stat used to determine talent and effectiveness. ERA shows trends and provides a guideline to see if a pitcher performs above or below average. The ERA Champion is recognized at the end of every MLB season, and a pitcher’s ERA is frequently used as a fundamental criterion for the Cy Young Award race. ERA has some drawbacks, but it is still an important number for pitchers to watch.

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