In the 1950s, a group of readability experts thought the formulas needed a shake-up. But, how did they modernize them to make their own formula, and how can it best be used?

What is the Powers Sumner Kearl formula?

The Powers Sumner Kearl formula is a readability formula which calculates a US grade level to indicate how readable a text is. It uses the number of words, sentence length and number of syllables as variables.

Where did the formula come from?

The formula was created by R D Powers, W A Sumner and B E Kearl. They published it in 1958 in a journal named A Recalculation of Four Adult Readability Formulas.

The formula is as follows:

Reading age = 0.0778 (average sentence length) + 0.0455 (number of syllables) + 2.7971

In writing about the creation of the formula, Powers, Sumner and Kearl pointed out some flaws in previous readability research.

They argued that a lot of research at the time was based on comprehension tests which were published back in the 1920s.

Astutely, they pointed out that the outdated nature of these tests presented a problem. The 1920s comprehension tests used for the creation of contemporary readability formulas didn’t reflect continual changes in language and culture.

Powers, Sumner and Kearl were interested in an analysis which was as empirically accurate as possible.

Their aim was to modernize the existing formulas to reflect more recent comprehension tests that were available.

Comprehension tests are important in the creation of a readability formula because they support the validity of the formula.

Children’s reading abilities had changed between the 1920s and 1950s. Although reading instruction was focused on comprehension during this time, children weren’t taught phonics until Rudolf Flesch published a book called Why Johnny Can’t Read in the 1950s.

In the book, he argued that children should absolutely be taught phonics and studies since have proven the importance of connecting letters with sounds in early learning.

Powers, Sumner and Kearl were passionate about making sure readability formulas evolved alongside the evolving instruction of reading.

The difference in scoring after they modernized several formulas to create their own formula was just below a grade level.

Like us, they believed in ensuring the continued accuracy of readability tests by keeping the modern reader in mind.

At Readable, we keep in mind the reading habits of your audience today. Are you keeping your audience engaged with readable content? 

How can the Powers Sumner Kearl formula best be used?

This readability formula is considered most appropriate for children between the age of seven and ten. In US grade levels, this is between second and fourth grade.

The formula is not considered useful for children’s literature above a reading age of 10.

This is a similar age range to the Spache readability formula.

Readable supports the Read Aloud campaign which encourages parents to read to their children for 15 minutes per day - that’s over 400 hours of reading over five years.

It’s been shown that reading aloud to children encourages better educational outcomes.

Therefore, it’s important for parents and teachers alike to know the most suitable text which can be comprehended as well as heard.

So, early in the child’s development, if they’ve been read aloud to they will have a good foundation of vocabulary, knowledge building, pre-literacy skills, love of reading and much more.

By the time they’re between second and fourth grade, they’ll be able to read on their own and read silently.

Choosing the right books for this time is crucial. If you give a child a text which is too easy, it won’t fuel their interest in reading - they’ll grow disinterested.

If you give a child a text which is too hard they’ll get discouraged.

If you choose one that’s just right, like the warm bowl of porridge in the Three Bears story, they’ll be able to comprehend the text whilst still being able to challenge themselves.

This will fuel their passion for reading and build the language skills and confidence they’ll need for middle school and beyond.

Using the Powers Sumner Kearl formula on ReadablePro will accurately determine whether the book the child’s reading is that perfect bowl of porridge.

Laura Kelly

Laura is a content writer and customer success champion at Readable. She's a Literature MA graduate who loves poetry, a good coffee and 35mm photography.