ERA Calculator
Find a pitcher's earned run average.
Results update as you type.
How it works
ERA, earned run average, is the most widely used measure of a baseball pitcher's effectiveness, and this calculator finds it from earned runs and innings pitched. You enter the number of earned runs a pitcher has allowed and the innings they have pitched, and it returns the ERA. The statistic expresses run prevention on a per-nine-innings basis, the length of a standard game, by multiplying earned runs by nine and dividing by innings pitched. This lets you compare pitchers fairly regardless of how many innings each has thrown, since a reliever with few innings and a starter with many are placed on the same scale. Only earned runs count: runs that score due to fielding errors or passed balls are unearned and excluded, so ERA isolates the pitcher's own responsibility. A lower ERA is better, indicating the pitcher allows fewer runs; historically an ERA under 3.00 is excellent, around 4.00 is average, and above 5.00 is poor, though the norm shifts with the era of play and ballpark. Note that innings pitched are often recorded in thirds, so two-thirds of an inning is entered as 0.2 in traditional notation but should be converted to a true decimal, roughly 0.67, for an exact calculation. Enter earned runs and innings pitched to compute the ERA.
ERA = (earned runs × 9) / innings pitched
Earned run average scales the earned runs a pitcher allows to a standard nine-inning game. It multiplies earned runs by nine and divides by the innings pitched, giving the average earned runs the pitcher would surrender per full game. Lower ERA means better run prevention, and it excludes runs caused by fielding errors.
Source:Baseball statistics
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter earned runs allowed and innings pitched.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Earned run average updates instantly as you type — no button to press.
Frequently asked questions
What is ERA in baseball?
ERA, or earned run average, measures how many earned runs a pitcher allows per nine innings, the length of a standard game. It is the classic yardstick of pitching effectiveness. A lower ERA means the pitcher prevents runs better, and it is calculated by scaling earned runs allowed to a full nine-inning game.
How is ERA calculated?
Multiply the earned runs allowed by nine, then divide by the innings pitched. For 30 earned runs over 180 innings, the ERA is 1.50. Multiplying by nine standardizes the figure to a full game so pitchers with different innings totals can be compared. The calculator does this instantly from your two inputs.
What is the difference between earned and unearned runs?
Earned runs are those a pitcher allows through hits, walks, and their own pitching, while unearned runs score because of fielding errors or passed balls that should have ended the inning. ERA counts only earned runs, isolating the pitcher's responsibility from the defense's mistakes behind them.
What is a good ERA?
Standards shift with the era of play, but generally an ERA under 3.00 is excellent, around 4.00 is roughly average, and above 5.00 is poor. Elite seasons dip below 2.00. Ballpark, league offense levels, and role also matter, so compare a pitcher's ERA to their league average for context.
How do I enter innings pitched with partial innings?
Innings are traditionally written with thirds, where .1 means one out and .2 means two outs. For an exact ERA, convert these to true decimals: one-third is about 0.33 and two-thirds about 0.67. So 180 and one-third innings should be entered as roughly 180.33 rather than 180.1 for accuracy.