Era Calculator – Earned Run Average

If you're a baseball coach, analyst, major league baseball player or just a curious fan, this ERA (Earned Run Average) calculator can be super useful for you. The ERA provides fundamental pitching statistic measurement in baseball — providing a standard method to determine the pitcher's effectiveness.

In this article, I will explain everything about Earned Run Average (ERA), what it is, how ERA and advanced pitching metrics, like WHIP (Walks plus Hits per Inning Pitched), are calculated, formula along with examples, and some FAQs.

What is ERA — Earned Run Average?

ERA in baseball represents the pitcher's effectiveness by calculating the average number of earned runs a pitcher allows per nine innings pitched. It excludes any runs scored due to defensive errors or passed balls, which are not considered in ERA calculation, making it a clean measure of the pitcher's performance.

A lower ERA means better performance, look an example below:

• Excellent: Below 3.00
• Average: Around 4.00
• Poor: Above 5.00

A Brief History of ERA

ERA was first introduced in the 1900s as baseball started to evolve from an offense-dominated game to one focused more on strategy and pitching. And making it popularised by British statistician Henry Chadwick, so it became a standard statistic in Major League Baseball (MLB) in the early 20th century.

Advanced analytics such as FIP and xERA offer additional context. Still, ERA remains the most trusted and reliable metric to determine a pitcher's ability to prevent runs.

How ERA is calculated — Formula with Example

The formula for the ERA is quite simple: Earned Runs are divided by inning pitched, and the resulting value is multiplied by 9 to give the ERA. The following is the mathematical form:

ERA = (Earned Runs / Inning Pitched) × 9

Where:

• ERA = Earned Run Average
• Earned Runs = The number of runs scored against a pitcher while excluding the runs that are the result of defensive errors.
• Inning Pitched = Innings can be fractional (for example, 7.1 = 7⅓ innings, 7.2 = 7⅔ innings).
• 9 in the formula represents the standard length of a game.

ERA Real-World Example

imagine a pitcher allowed 4 earned runs over 6.2 innings (6⅔ innings):

Step 1: Convert innings to decimal

• 6.2 in baseball ≠ 6.2 in math
• 6.2 = 6 + (2/3) = 6.6667 innings

Step 2: Apply formula

• ERA = (4 / 6.6667) × 9 = 0.6 × 9 = 5.4

Thus, we calculated the pitcher's ERA is 5.4.

An Advanced Pitching Metric — WHIP (Walks plus Hits per Inning Pitched)

WHIP (Walks plus Hits per Inning Pitched) is an advanced metric that complements ERA. It measures how many baserunners a pitcher allows per inning. The following formula is straightforward:

WHIP = (Hits + Walks) / Innings Pitched

Where:

• WHIP = Walks plus Hits per Inning Pitched
• Hits = Total hits allowed by the pitcher
• Walks = Total walks allowed by the pitcher
• Innings Pitched = Innings can be fractional (for example, 7.1 = 7⅓ innings, 7.2 = 7⅔ innings)

Unlike ERA, the WHIP is not calculated per nine innings, while a lower WHIP indicates fewer baserunners, generally suggesting better pitching. However, the WHIP league average usually falls between 1.30 and 1.40, while the elite pitcher records a WHIP under 1.00.

WHIP Real-World Example

Imagine a pitcher allowed 8 hits and 3 walks over 6.2 innings (6⅔ innings):

Step 1: Convert innings to decimal

• 6.2 in baseball ≠ 6.2 in math
• 6.2 = 6 + (2/3) = 6.667 innings

Step 2: Apply formula

• WHIP = (8 + 3) / 6.667 = 11 / 6.667 = 1.65

Thus, the pitcher's WHIP is 1.65, which is above the league average (typically around 1.30 to 1.40), showing the pitcher allows more baserunners than average.