Fog Index Calculator

Calculate the Fog Index of text to determine its readability and complexity

Input Parameters

Calculation Results

Calculation Formula

Fog Index = 0.4 × ((average sentence length) + 1.5 × (percentage of complex words))

Where:
Average sentence length = Word count / Sentence count
Percentage of complex words = Complex word count / Word count × 100

Average Sentence Length:

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Percentage of Complex Words:

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Fog Index:

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Readability Level:

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Fog Index Calculator Calculator Usage Guide

Learn how to use the Fog Index Calculator and understand its implications

What is the Fog Index?

The Fog Index is a readability test that measures the complexity of English writing. It was developed by Robert Gunning in 1949. The index is based on the number of words with three or more syllables per sentence.

How to Use the Calculator

  1. Enter the total word count of your text
  2. Enter the total number of sentences in your text
  3. Enter the number of complex words (words with three or more syllables) in your text
  4. Click the "Calculate" button to determine the Fog Index

Understanding the Results

The Fog Index ranges from 0 to 20, with higher numbers indicating more complex text:

  • 0-7: Very Easy to Read
  • 8-12: Easy to Read
  • 13-17: Standard
  • 18-20: Complex

Practical Applications

The Fog Index is particularly useful for technical writers, educators, and content creators who need to ensure their writing is accessible to their target audience. It helps determine if text is appropriate for a general audience, students, or professionals.

Example Calculation

Consider a text with 200 words, 50 sentences, and 30 complex words:

1. Average sentence length = 200 words / 50 sentences = 4 words per sentence

2. Percentage of complex words = (30 words / 200 words) × 100 = 15%

3. Fog Index = 0.4 × (4 + 1.5 × 15) = 0.4 × (4 + 22.5) = 0.4 × 26.5 = 10.6

4. Readability Level: Easy to Read (8-12)