Have you ever noticed that some writing is a breeze to read, while with other texts you may need to re-read several times to get the intended meaning? As it turns out, there’s a bit of a science behind that. And it goes beyond Flesch-Kincaid.

Since the 1800s, linguists and researchers have developed a number of different methods to assess the “readability” of a text. As the name suggests, readability measures the ease with which a person can comprehend a written text. Some factors used to measure readability include reading speed, the speed of perception and how quickly a reader becomes fatigued.

About Readability Tests

Basic measures of readability included ranking popular texts in a list, which is known as text levelling. This technique works well in books aimed at young children, but is less effective when evaluating texts written for an adult reader.

Vocabulary lists are another method of assessing readability, which helps match books to readers that are similar to their current reading ability. Again, this is preferred for use in children whose reading ability is still developing, as opposed to adults.


Among some of the more popular formulas is the Flesch-Kincaid test. Developed in 1943 by Rudolf Flesch, these readability tests are still so popular that Flesch-Kincaid is now one of the default readability options in Microsoft Word. It’s also used by the Yoast plugin for WordPress to determine a readability score for posts, like this:

Yoast readability

Technically, Flesch-Kincaid is comprised of two different tests. There’s a Reading Ease test, and a Grade Level test. However, in practical terms, these tests are essentially the inverse of one another; a text with a high reading ease score will be readable by a low grade level, and vice versa.

Without going into the complicated mathematical formulas involved, the Flesch-Kincaid tests primarily look at two ratios:

  • The average sentence length (total number of words in relation to the total number of sentences)
  • The average word length (total number of syllables in relation to the total number of words.)

It is relatively easy to assess writing using Flesch-Kincaid compared to other tests.

You can check your text against the Flesch-Kincaid formula using this online checker, or install a Chrome extension to check pages as you browse.


The Dale-Chall readability formula was developed by Ohio State University professor Edgar Dale. It’s harder to use than other reading tests, but arguably provides the most reliable results of any of the tests we looked at. It has a correlation of 0.93 with comprehension, compared with others that may score as low as 0.66.

The Dale-Chall formula uses a list of 3,000 “easy words” to evaluate readability. Several 100 word samples are taken from throughout the work. Average sentence length is computed in a similar manner to the Flesch-Kincaid readability test, and then the percentage of words not on the “easy word” list must be calculated. Together, these two numbers are input into a formula to give a score, which in turn correlates to a school grade level.

WordCoundTools provides full details of the Dale-Chall formula.

Fry Readability Graph

The Fry Readability Graph is one of the newer readability tests, developed by Edward Fry in 1963. The test has become one of the more popular readability formulas because of its ease of use, although it comes at the expense of being less reliable than other tests such as the Dale-Chall.

The average number of syllables and sentences per hundred words are calculated and plotted on a pre-made graph to determine readability.

Fry Readability Graph

Specialised Readability Formulas

You could look at other readability calculators designed for use in business:

Some of these are designed for very specific types of content. For example, the Linsear Write and Automated Readbility Index formulas are primarily used in technical authoring. There are many others we haven’t mentioned, including a clutch of formulas aimed at making text easier for children to read.

Choosing a Readability Formula

When determining the readability formula to use, it really comes down to personal preference. Hundreds of studies and much arguing among academics has taken place on the accuracy of various methods, but they will all give a good insight into your writing. And for the average user, writing non-specialised content, the difference in results between different readability formulas will be insignificant.

But when writing for the web, there are equally important layout and style rules that affect readability too.

Readability is About More Than Just Words

Readability is made up of other factors besides the words you choose. If you’re familiar with the abbreviation “TLDR” (too long, didn’t read), then you’ve likely encountered a giant block of text online that was formatted so poorly that you couldn’t bring yourself to read it.

Sometimes it doesn’t matter how simple the language used in the text is. There is a lot more to human psychology when it comes to how easy something is to read. With online content, readers have notoriously short attention spans. You really have to hook them early and keep them reading by frequently pulling them further in.

The text itself plays a significant role in online readability:

  • The font you choose, as well as the font size and how you vary it, will play a role.
  • The line height and length of your blog may impact how successful it is at getting people to read your text all the way through.
  • Keeping paragraphs short is key when writing online, as people will easily be intimidated by solid blocks of text. You can break things up with numbered lists or headings.
  • Bolding important words throughout your article for those readers who are just skimming can help
  • Eye candy will keep readers interested and give them some variation from just staring at the text. Mixing in some images or screenshots, along with graphics featuring quotes or excerpts will give your audience a brief intermission to digest what they’ve read so far before diving into the next paragraph
  • For longer posts, a table of contents is a must-have. Some readers may come to your page knowing exactly what they’re looking for, but don’t want to scroll through twenty pages to find what they’re looking for. TOC Plus is a great plugin for WordPress that can help you easily insert a table of contents into your post.

Quality is the Most Important Factor

With all this emphasis on readability, it can sometimes be easy to lose sight of the bigger picture. Keep in mind that the quality of your content is still the most important factor of your writing.

Achieving a high Flesch-Kincaid score can be tricky when writing about very high-level or technical subjects, which will always have a lower score than general business content. For example, technical blog posts almost always have a much lower readability score than general small business blogs. That’s perfectly fine. It’s about finding a balance between information and engagement.

Instead of scrutinising every text you write individually, it may be more helpful to look at the average readability score across all of your writing to identify your weakest areas.


Linguistic experts tend to agree that while readability formulas are ideal for determining the readability of texts that have already been written, they are not very practical for creating new texts or modifying existing texts after the fact. It’s quite the opposite, and often attempting to write to meet the standards of a readability formula can actually make your text harder to read instead of easier.

Learning to write for a new target audience takes a lot of work, and requires changing the entire voice and tone of your writing in addition to just choosing different simple words. In general, simply trying to write the way you speak can be an excellent way to make your writing easier to understand.

While readability scores can be beneficial for making small tweaks to your writing, it’s best to take them with a grain of salt and not obsess over them too much. Proofreading your work will give a general idea of the readability of your writing. If you’re still unsure, asking a friend to read your writing — or reading it aloud — can often provide more valuable feedback than simply plugging it into an automated readability formula.