Powers-Sumner-Kearl Readability Formula

Back in the day, in 1958, three guys created a powerful readability measure, the Power-Sumner-Kearl Readability Formula. They were R.D. Powers, B.E. Kearl, and W.A. Summer. This formula was published in a journal called A Recalculation of Four Adult Readability Formulas at the University of Wisconsin. Their readability formula, designed to improve reading by assessing readability level, was created mostly for the primary grades up to the 3rd-grade level. Their formula takes into consideration how many words are present, how many sentences there are, as well as the number of syllables.

Jonathan Gillham

It’s one of the best formulas to calculate the US grade level of a text sample

The formula uses simple measures and is suited for assessing readability levels for kids aged 7 to 10. It’s not considered an ideal educational measurement for children over the age of 10.

When creating their readability measure, Powers, Sumner, and Kearl pointed out flaws in previous research. They said lots of previous studies had been based on comprehension tests dating back to the 1920s. They worried that the old tests didn't reflect modern language and wanted to modernize the existing formulas.

Phonics was important

They noticed that kids’ reading abilities had changed a lot between the 1920s and the 1950s. A man called Rudolf Flesch published a book called Why Johnny Can’t Read in the 1950s. He was adamant that children had to be taught phonics to help them with their reading skills and their ease of comprehension.

There were studies that proved how important it was to connect letters with sounds in kids’ early learning

Powers, Sumner, and Kearl were passionate about creating a formula that would evolve with modern teaching and reading practices. Many findings of studies have shown how important connecting letters is with sounds in early learning. It was discovered that reading aloud to children leads to better education outcomes.

It is also important that kids understand what they could hear to fuel their passion for reading. It helps build reading skills and confidence. Reading aloud understandable texts to kids by choosing the correct reading level means children take on the right challenges and fuel their passion for independent reading.

Today, using the Powers, Sumner, and Kearl Reading Formula along with Readable can accurately determine whether the right age group goes hand-in-hand with a text's grade-level readability based on the complexity of prose.

How do you use the Power-Sumner-Kearl Readability Formula?

o Choose a sample passage that consists of about 100 words.

o Then calculate exactly how many words and sentences are in the given text.

o Then divide the number of words by the number of sentences. This will give you the ASL, which is the Average Sentence Length.

o Then you apply the formula to get a readability score. Don’t worry; here is everything to know about the formula.

o You can also use the Powers-Sumner-Kearl Readability Calculator. This will give you the grade level of your text based on average sentence length and syllable count using the formula's computation of readability.

Why use a Readability Formula such as the Powers-Sumner-Kearl one?

In a nutshell, it helps you write better. Readability doesn’t have to do with the literacy or legibility of writing. It's described as "the ease of understanding or comprehension due to the style of writing." It is a means of measuring text difficulty to help assess if it will reach the average reader of your target audience.

Authors who are writing text consider readability measures as an easy way to judge the reading difficulty of a text. Most readability formulas are based on the difficulty of words and the difficulty of sentences.

Why readability formulas are important

Classic readability formulas help ensure that readers understand the text they are reading. Scientific and mathematical principles are applied to analyze levels of readability. Researchers and writers have been using these formulas since the early 21st century. Other traditional readability formulas besides the P-S-K are:

o Rudolph Flesch Reading Ease Formula

o Flesch-Kincaid Readability Score

o J. Peter Kinkaid's Flesch-Kinkaid Index

o Robert Gunning's Fog Index

o The SMOG Readability Formula

o Fry's Readability Graph

o New Dale-Chall Formula and Dale-Chall List

o FORCAST Readability Formula

o Spache Readability Formula.

Are readability formulas well used?

Lots of organizations use formulas to determine if a complex text for their staff is readable from an adult reader's point of view. If complex English reading materials aren't readable, then what was the purpose of writing them?

With a readability formula, you are able to prepare readable text, saving you time and money that you would have wasted writing a complicated document that nobody understands.


The Powers-Sumner-Kearl Readability Formula was created by top researchers using valid measures of readability to assess the reading level of texts. They wanted to modernize the existing readability formulas. Their first offering was published in a journal called the Journal of Educational Psychology in 1958.

Today, this readability measure has proven highly useful for children between the ages of 7 and 10. The key features of this excellent readability formula are the number of words in a sentence, the average length of the sentence, and the number of syllables to determine if a text is understandable and easy to read!

Jonathan Gillham

Founder / CEO of Originality.AI I have been involved in the SEO and Content Marketing world for over a decade. My career started with a portfolio of content sites, recently I sold 2 content marketing agencies and I am the Co-Founder of, the leading place to buy and sell content websites. Through these experiences I understand what web publishers need when it comes to verifying content is original. I am not For or Against AI content, I think it has a place in everyones content strategy. However, I believe you as the publisher should be the one making the decision on when to use AI content. Our Originality checking tool has been built with serious web publishers in mind!

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