Readability FAQ
How readability scores are calculated, what each score means, and how to improve them.
Every mainstream readability formula measures the same two things: how long your sentences are, and how complex your words are. Flesch Reading Ease and Flesch–Kincaid use syllables per word; Gunning Fog and SMOG count "polysyllabic" words of three syllables or more; Coleman–Liau and ARI use characters per word instead, which makes them more reliable on text with unusual spelling.
That shared basis is why the scores move together, and why the same two edits — split long sentences, swap Latinate words for Anglo-Saxon ones — improve all of them at once. What the formulas don't measure is argument structure, jargon density, or whether the text is any good.
What is a good Flesch reading ease score?
For most online writing, aim for a Flesch Reading Ease score of 60–70. That's the band where Reader's Digest, well-edited blog posts, and most news writing cluster.
Below 60 the writing reads as effortful for general audiences; above 70 starts to feel oversimplified. Technical and legal writing legitimately scores below 50.
Read more: Flesch Reading Ease explained.
How do I improve my readability score?
Three high-leverage edits, in order:
- Replace one polysyllabic word per sentence with a shorter synonym (utilize → use, demonstrate → show).
- Break sentences longer than 25 words at coordinating conjunctions.
- Cut "very" and "really" and most adverbs.
For the full list of nine practical edits: How to improve your readability score.
What is the Gunning Fog Index?
The Gunning Fog Index, developed by Robert Gunning, is a readability formula that emphasises polysyllabic words. It outputs a US grade level: a Fog score of 8 means an eighth-grader could read the text. Formula: 0.4 × (words/sentences + 100 × complex_words/words). See Readability grade levels explained.
What is SMOG readability?
SMOG (Simple Measure of Gobbledygook) is a readability formula that counts polysyllabic words across 30 sentences. Designed for healthcare and patient-education writing where misunderstanding has consequences. Tends to score conservatively (higher grade level) than Flesch–Kincaid.