The Maths That Helps You Write Better English

Readability, Accessibility and Enjoyability

The language you use for business writing may have perfect grammar. Your choice of words may be precise. Your spelling exact. You may adhere to all the rules of business writing you hold as important.

But is your writing enjoyable? Or, at least, readable?

Enjoyability may be subjective. After all, one person’s poetry is another person’s polemic.

Readability can be worked out using a bit of maths.


A silhouette of a person writing mathematical equations on a white board
Photo by ThisisEngineering @ Unsplash

The Maths of Words

There are several formulae commonly used to grade copy for its readability. While there are some who oppose such metrics, readability scores are widely accepted and used by many professional organisations across the world.

That isn’t to say that readability should be taken at face value. Mathematical equations don’t consider creativity. If you only write to adhere to readability scores, your copy will lack any personality. Readability may come at the cost of enjoyability.

But using these tests as an input can help make your business writing better.


The Digital Context

Readability and accessibility are often talked about in the same breath. They both exist to enable as many people as possible to understand content.

Accessibility relates to the visualisation of content. It’s about fonts, colours and layouts and is clearly relevant to digital writing.

Readability predates the internet. Many of the tests used today were created over 70 years ago. The Gunning Fog Index was developed by a publisher in 1964. The SMOG (Simple Measure of Gobbledygook) Index by a London psychologist in 1969.

Probably the most common readability score is Flesch(-Kincaid). Its original outing as Flesch Reading Ease was created in the 1940s. By the 70s, it was developed, and used, by the US Navy as the Flesch-Kincaid Grade Level.

Flesch and Flesch-Kincaid are the readability scores installed in Microsoft Word’s Editor tool and used as a benchmark by the UK Government. We will use these to look at readability more closely.


Readability Formula

All have a slightly different way of getting to the same outcome. This means the results you get will span a range if you run copy through more than one test. But the approach is, more or less, the same.

Complexity is defined by number of syllables per word, and number of words per sentence. By counting the averages of both and applying a multiplier and doing a bit of addition and subtraction, a score is generated.

For example:

Flesch Reading Ease

206.835 – 1.015 (total words ÷ total sentences) – 84.6 (total syllables ÷ total words)

Flesch-Kincaid Grade Level

0.39 (total words ÷ total sentences) + 11.8 (total syllables ÷ total words) – 15.59

(Before you start counting syllables, all the tools are widely available online to do it for you. This site allows you to choose a selection if you wish.)

The score equates to an American High School grade. The assertion being that the copy should be easily understood by most children at that grade.

You may think that this doesn’t apply to your business writing. You wouldn’t expect your teenage child to be interested in your data analysis presentation. That’s true. But even when the subject is complex, the language you use should still be simple.

Research shows that the more educated the person, the greater their preference for plain English. It’s the same when knowledge is specialist. Technical terms – which you wouldn’t expect your average child to understand – are fine. Using them unnecessarily, or surrounding them with wordy description, is not.


Understanding Readability Scores

Judging text against the US Grade system can be confusing, especially for us Brits. You can ignore this if you just look at the score given by the Flesch Reading Ease test.

The formula scores text from 0 to 100. The higher the score given by this formula, the more accessible it is likely to be to more people.

Readability tests do not consider the meaning of words. So copy that is filled with short and complex words may score as more readable than text filled with simpler, but longer words.

But running copy through a readability test often highlights those bullshit words that have a tendency to slip in "accidentally".

How to Write Your Copy Readable

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To illustrate, we took an example of standard website copy. The sort of text that wouldn’t seem out of place on the home page of any marketing agency.

This copy has been generated by the website builder, Wix. By answering a few simple, topline questions – such as what your business does and what it is called – Wix will provide the copy for you to use.

And many companies have done just done that. Google this copy and you will find it written, verbatim, on multiple marketing agency websites. This should give you a clue to how baseless the words are.

The Copy

“Since 2012, we have helped companies strategise and implement their creative visions.

Our growing marketing agency is driven by passionate thinkers who work closely with each brand to create ideas and strategies that produce unparalleled results.

We love content and design but thrive on the data necessary to succeed in a digital world.”

You might think this copy is quite simple. You will recognise the language if you have ever worked with an agency.

So you may be surprised to know that it has a Flesch-Kincaid score of only 43.6.

The formula looks at sentence length and number of syllables. Here it’s clear that the 24-word sentence in the middle is impacting the score. Looking at the readability of that paragraph alone, the score goes down to 34.4.

The first thing to do is break up that sentence:

Our growing marketing agency is driven by passionate thinkers. We work closely with each brand. We create ideas and strategies that produce unparalleled results.

Without changing the words, readability for the entire text has increased to 50.8. The paragraph itself has gone up to 50.6.

That’s 47% more readable just by making those small changes.

The other factor is the syllable count.

Interestingly, the score is being impacted by the sort of words you may have on a winning bullshit bingo card. The words that add absolutely nothing. The words that are just wallpaper. The words we are all guilty of writing, even if we ignore them when reading.

Overblown words like ‘strategise’ and ‘implement’, instead of ‘think’ and ‘do’. Or ‘creative visions’ rather than ‘ideas’.

Unnecessary adjectives like thinkers (people) who are ‘passionate’. Or results that are ‘unparalleled’.

At best these are ridiculous. You would never hear of teams being nonchalant.

At worst they are lies.

To be truly unparalleled means these results have never been equalled. That may happen. But only very occasionally. To use the statement in this way is an outright lie.

So the second task is to remove or replace any words that you would struggle to define to your Nan.

Let’s apply that thinking to just the second paragraph again.

Our team loves to listen. They get excited by new challenges. These excitable listeners work with brand teams to find the right solution to your unique problem.

The readability score for that paragraph has now increased to 69.2. That’s almost exactly twice as readable as the original. The readability of the whole piece is now 59.5.

Clearly, we need to apply the same approach to the opening and closing. How about something like this:

“Since 2012, we’ve helped brands to shape their thinking and bring their ideas to life.

Our team loves to listen. They get excited by new challenges. These excitable listeners work with brand teams to find the right solution to your unique problem.

A solution that has the content people read. A solution that is designed to attract. All backed by the data to give you the results you can be proud of.”

Clearly this is lipstick on a pig. There is no real depth to anything as there is no real agency we are writing for. We have attempted to neither add anything nor take anything away from the original content. And we have increased the total word count by only 15%.

With those caveats, for readability alone, this version gets a score of 77.7.

It is still vacuous bullshit. But at least this vacuous bullshit is readable.



  • Readability tests are mathematical, and don’t allow for creativity.

  • The score you get should be relative to your audience. But…

  • As a rule, a score of around 70 is fine for most audiences.

  • A score less than 50, means it’s likely you’re being overcomplicated.

  • Less than 40 and you should really consider rewriting or revising.

  • Use readability scores to help highlight lengthy sentences and overcomplicated words.

  • Readability tests can also be used to flush out the bullshit bingo words.

  • You can enable readability in Word by following the steps here.

  • You can run copy (up to 3000 words at a time) through seven readability tests here.



If you’re curious, this article scores 60.7, which is lower than I would like. However, this is impacted by two things out of my control: the repeated use of the five-syllable word ‘readability’ and the example of bad copy.

Remove both and it scores a perfectly acceptable 68.4.


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