Automated Readability Index (ARI)

One of the readability tests that was developed early in the 20th century is the Automated Readability Index or ARI. There was a desire in many US industries for improved readability. So in 1967, the ARI was developed, particularly for military use. The purpose of the ARI was to monitor readability on electric typewriters. Remember, this was before the digital age. The ARI became a welcome way to measure readability. Nobody wanted to do the readability score calculations manually so this was a great relief! The ARI involved a special tabulator called the Readability Index Tabulator. This was attached to the typewriters of the day for the testing and real-time monitoring of readability accuracy. It was Mr. Robert Roettele who designed the Automated Readability Index tabulator.

The job of the Automated Readability Index

The ARI shows a person the breakdown of grade levels needed to understand a certain text. It does the job of accounting for the difficulty of words. A factor of characters that has been established in the past is that the more characters that make up a word, the more difficult it is to read.

Apart from considering specific words, the ARI will also assess sentence difficulty; i.e. the number of words that make up a sentence. To establish these two things, a readability formula is needed, which is called the Automated Readability Index formula. You need this formula for using the ARI – and it looks very complicated!

This is the formula

4.71(characters/words) + 0.5(words/sentences) – 21.43

This formula provides the Automated Readability Level of your text. The result will be the same as that of the US grade level required to understand the text. If, for instance, you got a score of 6, the text you are reading would suit someone in the 6th grade.

 Read more about the formula here. You will also find a conversion table here showing the results you would get from the ARI.

But where do you use such an index?

The ARI was specifically developed to determine whether their studying manuals and other high-tech reading material were fully understood by the personnel. It is still used quite a lot in different sectors of the military today.

Readability matters a lot

The ARI can be used for quite a lot of text varieties. If you like the idea of using this test, you can assess your own novels, blog posts, and essays using it. You can understand why text clarity is so important in every kind of reading material if you want to reach a wide target audience and keep them interested.

Do you know what readability is?

Readability is the measure used to discover how easy it is to read a piece of text. How readable your text is will depend on how complex the text is and how legible it is. Readability is key because accessible and reliable content builds the trust of the audience.

Why is readability so important?

Readability is important because in Google’s eyes, it’s a key ranking factor. If the average person finds website content too difficult to read, they’ll click on another website. Content that is easy to read will be easier to navigate and readers will be encouraged to stay on your page. This, in turn, improves bounce rates.

Did you know that there has been an increase in voice search on the internet over reading text? People these days are more interested in watching short videos than reading stuff that has long sentences and complicated words!

Can you improve your readability?

You will discover that the ARI is much the same as other readability tests, such as the Flesch Reading Ease and the Coleman-Liau Index.

The easiest way for you to improve your readability skills on all these tests is to write in a clear and simple way. Try to avoid using long words and technical jargon. Simple sentences that convey the message are best. If you want to reach a bigger audience, stick to using conversational English.

Don’t forget there’s a calculator to calculate the readability of your text

This will be able to calculate the readability of your text straight away so you can edit accordingly. Check it out here. It is designed to measure just how easy the text is to understand.

The ARI will give you an estimate of which US grade level is an approximate representation of the literacy level needed to understand a piece of text. So say, for instance, you scored 10 for your text. That means it can be read and understood by high school students.

Nobody might be reading the blog posts that you are putting on your website

You might have noticed that you are not getting any traffic from Google. Did you know that one of the biggest reasons for this is readability? When people gaze over an article and they see long sentences, complicated words, and walls of text to wade through, they bounce away to something else. So what gets the most attention? The answer is simple – precise, simple, and readable stuff.


The ARI is an excellent way to measure your writing for ease of reading. This is particularly important in marketing content, blogs, and website niches, and it can also be used for speeches and presentations. If you want to attract readers and keep their attention for longer, adjust your work to lower your score using the ARI.

All Readability Tests:

Here is a list of all readability tests.

Jonathan Gillham

Founder / CEO of 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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