FORCAST Readability Formula

Everybody wants documents that people are going to find easy to read. You want the potential readers of the documents to understand them by the way they send information back to you. To do this, plain language is needed. You have probably heard about school grade levels and readability levels from articles on common readability formulas such as the FORCAST Readability Formula. You probably know all about readability metrics online. They help you get your text down to a particular grade level.

Jonathan Gillham

Plain language is required if you want to meet your audience’s needs

The target grade level will depend on who your audience is, of course. The goal is to choose words that your readers are familiar with. The grade level readability score from a readability checker such as FORCAST is based on the average length of sentences and words.

There are quite a lot of different reading formulas, and they can vary a bit. Generally, they assume that longer words, harder words, and longer sentences make for harder reading.

What do reading formulas like FORCAST do?

Reading formulas can assess the clarity of texts for audiences around the world. Because most readability formulas are simple, they are relatively easy to use, which helps makes them reliable. They generally involve counting the syllables and words in a sentence.

Let’s look at what the FORCAST formula is about

The FORCAST was designed for the readability level analysis of technical documents such as forms, training manuals, or surveys.

Here is the FORCAST formula:

o Grade level (GL) = 20 − (N / 10)

The “N” in the formula is the Number of single-syllable words. The word sample is 150 words long.

How to work out the formula

  1. Select a text that consists of around 150 words.
  2. Next, count the number of single-syllable words in your text.
  3. Now divide the number of single-syllable words by ten.
  4. Then subtract your answer from twenty.

The FORCAST Formula doesn’t rely on complete sentences – it uses only a vocabulary element. Also, it is not like a lot of the other formulas. Why? - Because a lot of the other formulas were designed for use in schools, but not the FORCAST. It isn’t able to calculate below a 5th-grade level.

The origins of the FORCAST Formula

In the 1970s, there was a trend of new readability formulas being created to determine the reading levels of texts. FORCAST was the result of this trend.

FORCAST was created from a study done by HumPRO. HumRRO was founded to conduct behavioral science research. It developed training methodologies, tools, and applications for use by the U.S. Army.

The Army needed to find a unique answer to help in improving their training documents. It was meant to help the new personnel who arrived in the Army. That’s why FORCAST was created, and it proved to be the perfect solution.

John Caylor, Thomas Sticht, and J. Patrick Ford were assigned to improve the training documents in 1973. Their research was on Vietnam draftees entering basic training. The FORCAST Readability Formula was created from their study. It was published in a journal called Literacy Discussion.

The FORCAST Readability Formula is considered ideal for multiple-choice quiz contests, entrance forms, applications, and more. The U.S. Air Force approved the FORCAST Readability Formula in 1977 because it was so easy to use.

What is FORCAST useful for then?

FORCAST is a formula that was created to focus on functional literacy. Functional literacy is “the ability to identify, understand, interpret, create, communicate, and compute.”

A result from FORCAST is a U.S. education grade

If you are not writing for the public, then FORCAST runs slightly higher than the other reading formulas. If you’re a technical writer, then naturally there will be some essential terms that will need to be included.

For a FORCAST grade, it is recommended that writers aim for a grade of 9-10.

The values correspond to the number of years of education

A FORCAST grade is used to indicate how difficult a text is to read. It is based on the number of "easy" words that have just one syllable in a sample of text containing 100-150 words. The values correspond to the number of years of education a reader needs to understand the text.

For example, a value of 6 would correspond to 6th graders of 11-12 years old. 12 would correspond to 12th grade.

Look at how the values are interpreted

It is important to note that FORCAST is not recommended to assess primary school reading text.


In 1973, a study was authorized by the U.S. military of the reading skills required for various military jobs. These reading skills were produced by the FORCAST formula. The FORCAST formula only uses a vocabulary element. This makes it handy for texts that don't have complete sentences.

The FORCAST formula was found satisfactory for reading material in the Army and easy enough for staff to use without requiring special training or equipment.

Today, the FORCAST formula is an asset to any technical writer. It has proven to be a very valuable tool for questionnaires because a good FORCAST score on a survey makes the text easier to read.

Jonathan Gillham

Founder / CEO of Originality.AI 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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