To calculate earned run average (ERA) of a baseball player, just use the following formula:

Earned run average = (Number of earned runs × 9)/(number of innings pitched)

The formula above applies only to pitchers and it is used to determine how good a pitcher is.

The formula is used to find out how many runs a pitcher allows in a baseball game.

The lower this average, the better the pitcher is at not allowing runs in the game

Pitchers usually practice a lot to keep this number as low as possible.

When computing this average, we usually round answers to two decimal places

A baseball player had the following performance:

Allowed 4 runs

15 innings pitched

Earned run average = (Number of earned runs × 9)/(number of innings pitched)

Earned run average = (4 × 9)/(15)

Earned run average = (36)/(15)

Earned run average = 2.4

After rounding the answer to two decimal places, we get earned run average = 2.40

A baseball player had the following performance:

Allowed 7 runs

34 innings pitched

Earned run average = (Number of earned runs × 9)/(number of innings pitched)

Earned run average = (7 × 9)/(34)

Earned run average = (63)/(34)

Earned run average = 1.852941

After rounding the answer to two decimal places, we get earned run average = 1.85

A baseball player had the following performance:

Allowed 5 runs

32 innings pitched

Earned run average = (Number of earned runs × 9)/(number of innings pitched)

Earned run average = (5 × 9)/(32)

Earned run average = (45)/(32)

Earned run average = 1.40625

After rounding the answer to two decimal places, we get earned run average = 1.41

If you are a baseball coach, you may want to choose the player in example #3 because his average is lower.

However, no one so far was able to get an earned run average of 1.41. The ERA by the player in example #2 is close to what top players of all time were able to meet