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What Is the Automated Readability Index?

In order to effectively communicate with your intended audience, it’s important to understand their readability expectations. If you’re writing to a group of businesspeople, it would probably look a bit different than if your text is geared toward elementary school students. On this page, we’ll discuss the Automated Readability Index (ARI), what it means, and how you can improve the readability of your website.

What is the Automated Readability Index?

The automated readability index is a readability test designed to measure the how easy your text is to understand. Similar to other popular readability tools, the ARI gives you an estimate of the U.S. grade level necessary to comprehend a passage of text.

For example, if your ARI score is 10, then your text should be understood by high school students.

ARI is derived from ratios that represent word difficulty (number of letters per word) and sentence difficulty (number of words per sentence).

Most readability scores consist of two factors. The first factor relates to sentence structure, and typically measures the average number of words per sentence. Readability indices also take into account word structure, and are generally based on the average number of syllables per word or the proportion of easy words determined by referencing a word list.

Automated Readability Index formula: 4.71 x (characters/words) + 0.5 x (words/sentences) – 21.43.

What does my score mean?

Your Automated Readability Index score approximates the age needed to understand the text. For a breakdown of grade levels in the U.S., you can reference this chart:

  • 5-6 yrs. old — Kindergarten
  • 6-7 yrs. old — First Grade
  • 7-8 yrs. old — Second Grade
  • 8-9 yrs. old — Third Grade
  • 9-10 yrs. old — Fourth Grade
  • 10-11 yrs. old — Fifth Grade
  • 11-12 yrs. old — Sixth Grade
  • 12-13 yrs. old — Seventh Grade
  • 13-14 yrs. old — Eighth Grade
  • 14-15 yrs. old — Ninth Grade
  • 15-16 yrs. old — Tenth Grade
  • 16-17 yrs. old — Eleventh grade
  • 17-18 yrs. old — Twelfth grade
  • 18-22 yrs. old – College

Unlike most readability measures, ARI takes into account characters per word instead of syllables per word. This is because the number of characters is more accurately interpreted by computer programs.

If your ARI doesn’t accurately reflect the age or grade level of your target audience, you may need to revisit your text and make the necessary edits to ensure your writing resonates with the intended target.

Why is readability important?

In order to appeal to your target audience, your text needs to meet their readability expectations.

Are you writing to children or adult readers? Are your readers experts in the material?

If you’re writing about biology, you will probably want to alter the text if you’re writing to med students as opposed to high schoolers.

It’s also important to understand the intent of your readers. People reading for recreation will likely be interested in less complex material than those conducting research about a particular topic.

Understanding the readability expectations of your audience will help to keep people on your website for longer periods of time, increase engagement with your content, and lower bounce-rates.

Want to improve your score?

Want to evaluate and improve the readability of your website?

With our free readability test tool, you can check your ARI score with the click of a few buttons. Simply enter the URL of your website, and we’ll provide easy-to-understand results that help you estimate the effectiveness of your site when it comes to reaching the intended audience. We’ll also give you a checklist for improving the readability of your website.

Make sure your writing resonates with the intended audience. Test the readability of your work today and start improving the effectiveness of your website.