In the readability series so far, we’ve explored the differences between physical and conceptual readability, the importance of audience and context, and the value of making good assumptions.

None of those entries included math—but that’s all about to change.

Despite the average writer’s stated allergy to mathematics, much effort has gone into developing ways of measuring readability using algorithms and formulas. These formulas allow writers to quickly get a sense of how readable their work is. This final installment will introduce two of those formulas and briefly explore their benefits and drawbacks.

The Flesch Reading Ease

Perhaps the most popular of the readability quantifiers (it’s the one native to Microsoft Word) is the Flesch Reading Ease. This formula, pictured below, is based on sentence and word length.

The output of this algorithm is a score from 0 to 100, with 100 being the easiest to read and 0 being the most difficult (1).

Unsurprisingly, this formula has some problems. Nobody would argue that Ernest Hemingway’s The Old Man and the Sea is a simplistic document, yet it’s written using few syllables, short words, and short sentences. The complexity is mostly conceptual—it’s built into the literary devices that Hemingway uses—but the algorithm doesn’t recognize that complexity because it’s not looking for metaphors. It’s just crunching the numbers.

That’s not to say the Flesch formula isn’t useful, but it’s certainly not the only way to crumble the cookie.

The SMOG Score

Another way to quantify readability is the SMOG score (which rather fantastically stands for Simple Measure of Gobbledygook). Rather than interpret readability by factors of sentence and word length, the SMOG score measures the frequency of polysyllabic words (words that have more than three syllables).

The SMOG formula outputs a number that indicates what grade level the text is suitable for (based on the American education system’s grade levels). So, for example, a score of 3 indicates that the text can be understood by the average third grader (2). (For the curious, I tested this article and scored an 11.)

Readability indexes are particularly useful when writing for a lowest common denominator. If everyone from fifth grade up needs to understand what you’re saying, then you can run a SMOG check to see if you’re hitting a 5.

If you do that often, though, keep in mind the natural limitations of these algorithms. It’s easy to end up worrying too much about syllable count or sentence length, which can produce writing that’s stilted, simplistic, or inorganic.

The Peril of Ignoring Readability

Across our entire series on readability, there’s a consistent theme: It’s absolutely crucial for writers to consider how the audience will engage with their work. Failing to do so ignores the reason for writing in the first place, which is to transfer information from the mind of the writer to the mind of the reader.

I should add—if you’re writing something that nobody else is ever supposed to read, you can safely ignore everything I’ve suggested here. Otherwise, write to be read!

Tackling readability is daunting, but you don’t have to go it alone. McKinnon-Mulherin has a team of highly skilled writers and editors who can help you bridge the gap between your great ideas and your reader’s brain.

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For a full recap in our Readability blog series, check out the fifth and final post.