Determine the Difficulty of Text Using Readability Formula

How do you know how difficult a text is to…

How do you know how difficult a text is to understand? One way, often recommended by teachers and professors, is to use a readability formula. These easy-to-use formulas estimate the reading level or grade level needed by readers.

Calculating the readability formula is a helpful tool for evaluating texts. However, you must use it with care.

What Is a Readability Formula?

A readability formula is a scientific model which assists in determining the difficulty of a text. The formula was created to find the most efficient ways to write in a simple and accessible way.

The formula uses several variables to find the best combination of tone and vocabulary. Conditions such as the number of words, sentence lengths, and the number of phrases are taken into account to determine the most appropriate readability.

It groups text into levels of reading difficulty. It evaluates what type of writing needs to be deviated from to make reading easier.

Importance of Readability Formulas

When writing for your students or any audience, your text must be as accessible and easy to read as possible.

A readability formula can help you determine whether your text is easy to read and understand or if it requires some extra assistance.

Many different types of texts exist in various genres like articles, books, brochures, and more. Some are written for a very specific audience, some are meant to be read by the general audience. Others are meant to be read by children. These texts have different readability scores.

Therefore, readability formulas have great importance to the writers. They can determine the writing level necessary to make text readable.

boy wearing gray vest and pink dress shirt holding book
Photo by Ben White on Unsplash

How Does Different Readability Formula Work?

The readability formula consists of the following parts: words, syllables, sentences, and characters. The quality of a text is decided based on how simple or difficult it is to read.

One of the primary purposes of these formulas is to help determine text quality for accessibility. The application varies depending on what you want to do. They can be applied in different settings, such as learning, teaching, or client-based tasks.

Some of the most common readability formulas are as below:

Flesch Reading Ease

The Flesch Reading Ease measures the readability of a test by assigning a number between 1 and 100.

Reading a text is easier with a higher score. Any score between 70 and 80 represents a grade 8 reading level which means the text is easy to grasp for an average adult.

The formula for the Flesch Reading Ease score:

206.835 – (1.015 x Average Sentence Length) – (84.6 x Average Syllables Per Word).

This is one of the oldest formulas developed by Rudolf Flesch in the 1940s. He was a consultant at the Associated Press responsible for improving newspaper readability.


While most readability formula indicates a lower score as easier to read, the Flesch-Kincaid formula is the opposite. A higher score means more straightforward text.

The Flesch-Kincaid grade level score indicates the US grade level education a person must have to comprehend a specific text. Flesch-Kincaid Grade Level 8 text requires someone to complete eight years of education and reach eighth grade to understand it.

The formula to calculate the Flesch-Kincaid Reading Level score:

0.39 x (Average Sentence Length) + (11.8 x Average Syllables Per Word) – 15.59.

The formula is an amended version of the Flesch Reading Ease, developed in1970s by US Navy for ease of usage. They used it to calculate the readability of technical manuals in training.

SMOG Index

SMOG, the abbreviation of Simple Measure of Gobbledygook, is a readability framework. The formula was developed by sampling a text of 30 sentences, so it is best for text over 30 sentences.

Psychologist G. Harry McLaughlin developed this formula. It estimates the years the education any average person must have to understand a piece of text.

The SMOG grade is suggested to be calculated on a piece of 30 sentences or longer considering the following:

  • Counting a total of 30 sentences with10 sentences from the beginning, middle, and end each.
  • Counting complex words with three or more syllables.
  • Rounding the result to the nearest 10 after square-rooting the number.
  • Adding three to the result to determine the final reading level.

Gunning Fog Index

The Gunning Fog formula assigns a score between 0-20 which determines the education level needed to comprehend a text.

The formula to calculate Gunning Fog Level score:

0.4 [(words/sentences) + 100 (complex words/words)]

Eighth-graders easily digest a text of Fog score 8, and anything above 17 is aimed for graduate-level understanding.

Dale-Chall Formula

The Dale-Chall formula assigns a number based on the readability of content. It works using a list of simple and monosyllabic words that a fourth grader can comfortably read.

The formula to calculate the Dale-Chall readability score:

0.1579 × (100 × total difficult words ÷ total words) + 0.0496 × (total words ÷ total sentences)

The lower the test score, the more familiar the words to a fourth grader and the easier the text. The key aspect of this readability assessment is word familiarity.

Wrapping Up

The effectiveness of text discussion is determined mainly by the relative difficulty of the text. The difficulty is identified by various formulas, including Flesch, Flesch-Kincaid, SMOG, and Gunning Fog Index.

Each formula is tailored to a specific level, and each calculation requires readers to assess text based on a certain language level. Generally speaking, the lower the language level, the more complex the text is.

By using a readability formula, students can determine which text is more appropriate for a particular level or audience.

Frequently asked questions

Do readability scores matter?

The bottom line. In the world of reading, it’s easier than ever to determine your readability score and make sure you engage your readers.

Are readability formulas accurate?

However, readability formulas are not always 100% accurate. Someone has to put in great effort to write a text. However, the text may be unique in its contents, but it fails to serve its intended purpose of making the reader understand and use it.

What does readability score mean on Grammarly?

This score is a useful indicator of how easy it is for a reader to understand a piece of writing. If the writing is high, it means it flows easily and is easy to absorb. A reader may find it difficult to comprehend its message and key points if it is low.

What is the Flesch Kincaid method for readability?

A popular readability formula is known as the Flesch Kincaid Grade Level, which determines the reading grade level of a text. A US Navy organization named Flesch Reading Aid developed it. The Flesch Reading Ease score used to be converted using a table to the reading grade level previously.

What is Linsear write formula?

The Lensear Write readability formula is based on text. Words that are monosyllabic and strong verbs are scored. The score is calculated as follows: Consider a 100-word sample. Count all words with one syllable except ”the”, ‘is, ‘are,’ ‘was’ and ‘were’.

How accurate are readability Scores?

Seven of the eight readability formulas scored less than 49 percent, whereas the worst formula scored only 17 percent. It was accurate 79 percent of the time.

Is the Flesch Kincaid score accurate?

Additionally, it’s one of the few accurate measures that can be relied upon without too much scrutiny. The formula should be used on school texts. US Government Agency, including the US Department of Defense, have used it to determine readability standards.

What is a formula that estimates the reading level of text material?

These are useful to measure the difficulty of words and sentences in any written materials. You can choose from several dozen readability formulas, including the Fry formula, SMOG, Dale-Chall formula, and Flesch tests (Flesch-Kincaid and Flensch Reading Ea.

What does the Fry Readability Formula measure?

Reading a passage of text for an approximate grade is assigned through the Fry Readability Formula. Using the formula will help you decide how to edit your document so that it is more readable. It is not the organization or content of the text that determines the sentence structure.

Which readability tool gives a level of difficulty of a text based on sentence length and word length?

Reading tests such as Flesch-Kincaid are designed to measure readability in English by proving how difficult a passage is to understand. Flesch’s Reading Easy (Flesch-Kincaid) and Fletsch-Kennedy Grade Level are two tests.

How do you fix readability score?

  • Words that are short and easy.
  • Shorten your sentences
  • You can help us with your adjectives and adverbs.
  • Drop the jargon
  • Use reader-friendly fonts
  • Save your copy
  • Write your own work using readability formulas, and aim for grade level 7 or 8.

How do you determine the readability of a book?

If you want to know what level an author has, look at the cover or first few inside pages, since the information is often listed there. You can also test the contents and the first few pages to discover the subject of the book, which will let you know its reading ability.

Which readability formula is best?

Research has supported the findings of the study, suggesting that Dale Chall is the best approach for selecting the most appropriate texts for the grade level of students.

What defines readability?

Readability stands for how easy or difficult it is to read something. Text readability depends on the presentation (such as font choices, spacing or colors) and context (the words and sentences on the page).

How do you use readability formula?

Readability Formulas: How they work. The readability formulas are often based on long sentences and long words. Use readability formulas to count a few features of a text and put them together in a mathematical formula, and you get a reading age, usually a school grade.

Determine the Difficulty of Text Using Readability Formula

Pam is an expert grammarian with years of experience teaching English, writing and ESL Grammar courses at the university level. She is enamored with all things language and fascinated with how we use words to shape our world.

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