Automated Readability Index Calculator


Like many readability tests in the 1960s, the Automated Readability Index, also called ARI, was a product of revisions to further improve readability assessments in the US. It was designed in 1967 for the specific use of the military. Its primary purpose was to provide real-time readability monitoring on electric typewriters.

At the time before the digital age, the Automated Readability Index was a welcome and convenient way to measure readability than manual calculations. With the help of the Readability Index Tabulator (a specialized counter attached to a typewriter), this test’s accuracy is also less prone to error.


Like other readability tests during this time, the Automated Readability Index shows you the grade level a person needs to have to understand a particular text. But what makes it different is that it accounts for the word difficulty or the number of characters in a word instead of its syllables.

The idea is that the more characters that are present in a word, the harder it is to read.

Aside from words, it also accounts for the sentence difficulty the number of words in a sentence instead of consulting pre-meditated word lists.


The Automated Readability Index formula is pretty straightforward. You will need to use the formula:

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


Characters is the number of each letter and number.

With this formula, you can get the Automated Readability Level of your text. This result is also the equivalent of the US grade level one needs to understand the text. So if you get a score of 6, the text can be followed by most 6th graders or 11-year-olds and above.

Grade Conversion

Below is a simple conversion table showing the possible results you can get from the Automated Readability Index:

Score School Level Age
1 Kindergarten 5-6
2 1st & 2nd Grade 6-7
3 3rd Grade 7-9
4 4th Grade 9-10
5 5th Grade 10-11
6 6th Grade 11-12
7 7th Grade 12-13
8 8th Grade 13-14
9 9th Grade 14-15
10 10th Grade 15-16
11 11th Grade 16-17
12 12th Grade 17-18
13 College Student 18-24
14 Professor 24+


The Automated Readability Index is most used in the different sects of the military; Army, Air Force, and Navy. It was developed to determine whether their manuals and technical reading materials can be understood by their personnel. It is still a widely used readability assessment today.

However, the main takeaway that you can get from the Automated Readability Index is the idea that ‘readability matters.’ This test is versatile and can be used for a wide variety of text material. If you prefer to use this test, you can assess your blog posts, essays, novels, and the like with it. Clarity of text is essential in all kinds of reading materials if you want to reach a wider audience.

How to Improve Score

The Automated Readability Index is quite similar to several other readability tests like the Flesch Reading Ease and the Coleman-Liau Test. As such, improving your scores in this test is also comparable to how you need to improve your scores in the other tests.

The easiest way to improve your score is to write simply. Try to avoid big words and technical jargon whenever you can. Use simple sentence structures to convey your message. You should also write for your intended audience. If you want to reach a broader market, stick to conversational English.

Lastly, you can make the most of modern innovation and use an Automated Readability Index calculator. Calculate the readability of your text instantly and edit accordingly.

Further Readings


Automated Readability Index

The Automated Readability Index is:

See Grade Conversion Table to interpret the score.