ERA Calculator

Understanding ERA

Earned Run Average (ERA) is the most recognized statistical tool for evaluating a pitcher's performance in baseball. It represents the average number of earned runs a pitcher allows per nine innings pitched, providing a clear measure of their effectiveness on the mound.

Key Factors Explained

• Earned Runs: An earned run is any run scored by the opposing team that was not the result of a defensive error or a passed ball. It's a run for which the pitcher is held directly responsible.
• Innings Pitched: This is the total number of innings a pitcher has completed. Partial innings are represented by .1 for one out (⅓ inning) and .2 for two outs (⅔ innings).

The Formula

The formula for calculating ERA is simple and standardized across all levels of baseball:

The result is multiplied by nine to scale the pitcher's performance to a standard, full-length game.

Frequently Asked Questions (FAQ)

What is a good ERA?

A "good" ERA is relative to the league and era, but generally, an ERA below 3.00 is considered excellent, 3.00-4.00 is very good, 4.00-5.00 is average, and above 5.00 is below average.

How are partial innings handled in the calculation?

Each out is recorded as ⅓ of an inning. So, if a pitcher records one out in an inning, it's written as .1 innings pitched. Two outs are .2 innings. For the calculation, these are converted to their decimal equivalents (0.333 and 0.667).

What is the difference between a run and an earned run?

An official scorer determines if a run is earned or unearned. If a run scores due to a defensive mistake (like an error on a routine play), it is typically ruled unearned and does not count against the pitcher's ERA.

Why is ERA multiplied by 9?

Because a regulation baseball game is nine innings long. Multiplying the ratio of earned runs to innings pitched by nine scales the statistic to show how many runs a pitcher would hypothetically give up over a full game.

For a more in-depth guide, read our detailed article on this topic.