Use These Readability Scores to Get More Reads and More Leads

If no one is reading your blog posts, you’ve got company. You’re in the 90.63% of content that gets no traffic from Google. One big reason is readability. If it’s hard to read, they’ll find something easier to read. Bounce in 1.78 seconds. Sad.

Average eyes glaze over when they see long sentences, difficult words, and walls of text. It’s painful. Most of us don’t like pain. So we avoid it. In this case, we bounce.

Simple, precise, and readable documents get the most attention, influence the most readers, and lead to sharing and conversions. That what you want, right?

A readability score is a way to measure the ease of reading a piece of writing. Here, we’re focusing on marketing content like blogs and websites. But readability scales are useful for presentations and speeches, and even novels. Hemingway’s reading typically rates at a grammar school level. And he did pretty well for his adult self.

Adjust your work to lower your score and you’ll attract readers and keep them on the page longer. Google rewards that with higher rankings even if it doesn’t specifically admit to targeting readability.

Reading scales such as SMOG, Gunning Fog, and perhaps the king of them, Flesh­–Kincaid, do some math that gives you a clear idea of how readable your text is.

Adjust, simplify, shorten, and you’ll usually get people to read on.

Here’s an intro to readability and the most common readability tool formulas before you sit down to a keyboard and hammer out an oh-so-eloquent blog that no one reads.

What is “Readability”?

“Readability” is the property of being comparatively easy to read.

When you were in elementary school, you read “simple” books like Charlotte’s Web or Beverly Cleary’s Ramona books. These books have short sentences, easy narratives, and basic vocabulary. Kids love them, as do many adults. Ditto the Harry Potter series.

The ideas and lessons may not be “simple,” but the language is. That’s perfect for kids. It’s perfect for adults, too.

Later in high school, maybe you ran into 1984, with richer vocabulary, longer sentences, more words.

Or maybe you read The Catcher in the Rye, which is comparatively easy. That’s because Salinger was more readable than Orwell.

These are novels, though. Novels thrive on the author’s style and the art of words.

SEO blog posts typically don’t. White papers shouldn’t. Yet they often seem like dull novellas – big words, writers trying to “sound smart.”

Today’s busy people don’t have time or attention for Orwellian content. They want to scan, absorb, and, hopefully for you, they’ll go consume more. Readability is key.

The Most Popular Readability Metrics

You can use any of these as a guideline to make your writing more readable. We prefer the Flesch–Kincaid grade, but it’s fun to try different ones. Here’s how they work.

This simple site lets you drop in your text and calculate them. Other tools like Yoast SEO commonly include a readability metric, but they don’t give very good advice and we’ve found them to generally be a bit inaccurate and discouraging.

Flesch Reading Ease Score

Rudolph Flesch‘s formula starts from a set number and subtracts based on complexity and syllable counts. The result is a score between 1 (very hard to read) and 100 (very easy to read). The formula reads:

Flesch Reading Ease Score = 206.835 − (1.015 x average sentence length) − (84.6 x average syllables per word)

Harry Potter books rank between 75 and 85. Moby Dick, however, gets a 57, while a typical Harvard Law Review ranks in the 30s. Web copy is beast around 70–80. This is easy enough to read without intense attention but allows room for maturity.

Flesch–Kincaid Grade Level

There’s a lot of Flesch in the game. And that last sentence is just the type of self-indulgent folly you should get rid of in your blogs.

Here we have the same Flesch, plus John Kincaid; a pair of writers and educators. The Flesch–Kincaid grade may be the simplest form of readability tool. If you’re looking for a standard, this is it.

We swear by it. (Sometimes we swear about it after we spend 2 days writing something, only to find it’s Grade 11.)

This formula calculates average words per sentence and syllables per word to create a grade level. Grades indicate the U.S. student grades. So, a grade of 8 means an 8th-grade student should be able to read and understand it reasonably well.

Reading Grade Level = (.39 × average sentence length) + (11.8 × average syllables per word) − 15.59

A good target for websites and blog articles is around grade 6. That doesn’t mean you’re expecting a bunch of 12-year-old readers. What it means is that people can read it easily. They can scan through it, get the relevant information, and consume more.

A common excuse is that more technical or scientific text, by its nature will be less readable. While technical terms must be precise, and chemical compounds can be long, subject matter is no excuse for lack of readability.

Even a scientific manuscript can be written and edited achieve around a grade 8 or 9. Unless the peer reviewers insist that passive tense and big, unnecessary words are “more academic.” (They’re wrong!)

SMOG Index

An acronym for “simple measure of gobbledygook,” the SMOG Index is also based on an approximate grade level as a metric.

Introduced in 1969 by G. Harry McLaughlin, the SMOG Index was a key component of McLaughlin’s research about readability and clarity.

To use the index, a person should take 10 sentences in a row from the beginning, middle, and end of the text. That’s 30 sentences in total.

Next, count every word in the sentence list that has three or more syllables, including duplicates.

Take the square root of this figure and round it to the nearest whole number, and add three to this number to find the SMOG Index score.

More simply, the formula can be expressed as:

SMOG Index = 3 + (square root of polysyllabic count)

The SMOG Index number corresponds to grade levels up to 18, indicating college- and graduate-level reading levels.

SMOG Index

SMOG Score

Reading Grade Level

 1–6

 5

 7–12

 6
 13–20

 7

 21–30

 8

 31–42

 9

 43–56

 10
 57–72

 11

 73–90

 12

 91–110

 13

 111–132

 14

 133–156

 15

 157–182

 16

 183–210

 17

 211–240

 18

Like other readability scores, web content should aim for a readability grade of around 6–7, maybe 8 as a max. That strikes a balance of maturity and readability.

Gunning Fog Index

Attributed to American textbook publisher Robert Gunning, the Gunning Fog Index refers to his famous criticism of newspapers that Gunning believed were full of useless, “foggy” complex terms.

Gunning would go on to found the United States’ first readability firm in 1944. He spent his career working with dozens of newspaper writers and editors to streamline their publications.

The Gunning Fog Index takes a passage of at least 100 words and measures the ratio of words to sentences to derive average sentence length (ASL).

Next, count the number of three-syllable words (not including proper nouns or hyphenated words) and divide this number by the total word count to get a percentage of hard words (PHW). The Gunning Fog Index formula is then calculated by adding these two figures together and multiplying by 0.4.

Gunning Fog Index = 0.4 (ALS + PHW)

Although the Gunning Fog Index does not take into account that not all long words are inherently complex (e.g., “television”), it is relied on as a capable readability tool for SEO.

A Gunning Fog Index score of about 12 is usually considered too difficult for most people to read; leading newspapers like The Wall Street Journal typically come in at a 10 or 11, while TV Guide ranks around a 6.

Websites should try to create content that ranks at about 6–8.

Coleman–Liau Index

Rather than using the sentence length or syllable length of some other readability tools, the Coleman–Liau Index measures reading level by the complexity of characters. Linguists Meri Coleman and T. L. Liau believed that the character count of letters in words was a better indicator of complexity than syllable count.

Coleman–Liau Index = 5.89 × (characters/words) – 0.3 × (sentences/words) – 15.8

As with Flesch–Kincaid, the readability score from the Coleman-Liau Index refers to a grade level; 9.5 would be reasonable for a high school freshman.

As with the others, we’re shooting for somewhere around a junior high level, unless it’s highly technical and unavoidable verbose (that’s usually an excuse).

Automated Readability Index

Another calculation that combines the complexity of characters per word and words per sentence, the Automated Readability Index is another readability tool meant primarily to be used by computers and word processors for rapid results.

Automated Readability Index = 4.71 (characters/words) + 0.5 (words/sentences) − 21.43

As with the Coleman-Liau Index, the Automated Readability Index provides a number that corresponds to a grade level, and websites using this readability tool should not go below 9 or above 11.

Dale–Chall Readability Formula

One of the oldest readability grade measurements, the Dale-Chall Readability Formula dates back to 1948, when it was published by linguists Edgar Dale and Jeanne Chall.

Dale, an Ohio State education professor, and Chall, the founder of Harvard Reading Directory, took their inspiration from the Flesch scale, developing their formula for children above the 4th grade.

Unlike other metrics that look at word length, Dale–Chall looks at “hard” words, meaning words that would not be familiar to a 4th grader. Originally, the list included over 700 of these hard words; current editions list over 3,000 words in use, and that a 4th grader would probably not know.

These hard words are added up with a metric of average sentence length; this particular readability grade is valuable because familiar words are easier to read and understand than unfamiliar words, regardless of word length.

Dale–Chall Readability Formula = 0.1579 (percent difficult words) + 0.0496 (average sentence length)

If the percentage of difficult words is greater than 5% of the total, the formula includes an adjusted score:

Adjusted Dale–Chall Readability Formula = original score + 3.6365

Finally, Dale–Chall uses a table to gauge the reading level based on score:

Dale–Chall Readability Formula

Adjusted score

Grade level
4.9 and below

4 and below

5.0–5.9

5–6

6.0–6.9

7–8

7.0–7.9

9–10

8.0–8.9

11–12

9.0–9.9

13–15 (college/university)

10 and above

16 and above (college graduate)

Conclusion on readability formulas

The average American reads at a 7th- to 8th-grade level. It’s not to say they don’t have higher education; it just means this is what they easily understand. Globally, it’s not much different.

So write like a normal person.

Rethink if you really need to show off your big words.

Make your writing a pleasure to read. Not a chore.

Use readability tools to improve your site content, emails, and any textual interactions. You’ll likely see the reader move on to more of your content, and maybe even make a purchase.

This article, by the way, scores a Flesch–Kincaid Grade of 7.6. Hopefully, it was a pretty smooth read.

If you need help with simplifying your language, we love to chop. We love to reword. We love to make your readers love you. See some examples. Ask us how we can help.

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