What is the Readability Score and its Types and Formula?

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Have you ever wondered how readable your writing is? Readability score is a metric that measures the ease with which a reader can understand a piece of text. It helps to determine the level of difficulty and complexity of a written document. In this article, we will explore the concept of readability score, its types, and the formula used to calculate it.

There are several formulas and methods to calculate readability scores, but two of the most common and widely used are the Flesch-Kincaid Grade Level and the Gunning Fog Index. Here’s an overview of each:

  1. Flesch-Kincaid Grade Level (Flesch Reading Ease):
    • The Flesch-Kincaid Grade Level is a readability score that estimates the grade level required to understand a piece of text. The lower the grade level, the easier the text is to read.
    • Formula: The formula involves the average sentence length (ASL) and the average number of syllables per word (ASW).
    • Flesch-Kincaid Reading Ease = 206.835 – (1.015 × ASL) – (84.6 × ASW)
    • Higher scores indicate easier-to-read text.

2. Gunning Fog Index:

  • The Gunning Fog Index calculates readability based on sentence length and the number of complex words. It is another method to estimate the grade level required to read a text.
  • Formula: The formula involves the average sentence length (ASL) and the percentage of words with three or more syllables (ASW).
  • Gunning Fog Index = 0.4 × (ASL + ASW)
  • Higher scores indicate more complex and less readable text.


Readability score is an important tool for writers and educators to assess the readability of a text. By understanding the different types of readability scores and their formulas, writers can improve the accessibility and clarity of their writing. So, the next time you write a document, consider using a readability score to ensure that your message reaches your intended audience with ease.

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