What readability formulas measure
Every formula here counts two things: how long your sentences are and how long your words are. None of them understand meaning. They are still useful, because long sentences and long words are the two things that most reliably slow readers down, especially on a phone.
- Flesch Reading Ease (0–100, higher is easier) uses words per sentence and syllables per word. 60–70 is plain English; most good web copy lands between 60 and 80.
- Flesch-Kincaid Grade turns the same inputs into a US school grade. Grade 8 means a typical 13-year-old can follow it.
- Gunning Fog weights words of three or more syllables heavily. Business writing over 12 is hard going.
- SMOG estimates the grade needed to fully understand the text. It was built for health information and is most reliable with 30 or more sentences.
- Coleman-Liau and ARI count letters and characters instead of syllables, which makes them steadier on technical text.
What score to aim for
For a landing page or product description, aim for Flesch 60 or higher and a grade level of 7–9. That is not dumbing down. Readers who can handle grade 14 text still prefer grade 8 when they are skimming a pricing page between meetings.
How to raise the score
- Split long sentences. Anything over 25 words is listed above. Look for "and", "which" and "because" as natural break points.
- Swap long words for short ones. "Use" for "utilize", "help" for "facilitate", "start" for "commence".
- Cut stacked qualifiers. "Very", "really" and "in order to" add length without meaning.
Syllables are counted with a rule-based heuristic tuned for English, so scores can differ by a point or two from other tools. For counts and reading time, use the word counter.