The FORCAST readability formula analyses incomplete sentences. Find out what it is and how best to use it. 

What is the FORCAST formula?

The FORCAST formula is designed to analyse technical documents. These could be training manuals, forms and surveys.

The formula is:

Grade level = 20 − (N / 10)

Where N = number of single-syllable words in a 150-word sample

Unlike other formulas, it doesn’t rely on complete sentences. It only uses a vocabulary element. It is used for technical training material. It can also be used for surveys, questionnaires or multiple choice tests.

Unlike the many other formulas, it was not designed for school material. It can’t calculate below a fifth-grade level.

Where did the FORCAST formula come from?

In the 1970s, many new readability formulas were created. FORCAST was the result of this trend. It was the result of a study by HumRRO.

HumRRO was founded to research and develop tools for the US army.

They wanted to find a unique solution. One which would help improve their training documents for new personnel. FORCAST was a great solution for these non-narrative materials. This includes surveys, questionnaires and multiple-choice tests.

When is FORCAST most useful?

FORCAST is a formula focused on functional literacy. UNESCO defines functional literacy as:

‘The ability to identify, understand, interpret, create, communicate and compute.'

FORCAST is easy to use and helped them to improve their materials. The US Air Force officially approved FORCAST as a tool in the late 1970s.

The FORCAST formula is an asset to any technical writer. It is also an invaluable tool for questionnaires. A survey with a good FORCAST score is easier to read. The responses are therefore more reliable. FORCAST analyses incomplete sentences accurately.

The FORCAST result is a US education grade. FORCAST runs slightly higher than others if you’re not writing for the public. If you’re a technical writer, more of your language will be essential terms.

We recommend aiming for a FORCAST grade of 9-10.

Laura Kelly

Laura is a Marketing Executive at Readable. She loves coffee, literature, weightlifting and film photography.