Flesch Reading Ease and Grade Level Explained — With a Free Checker
What the Flesch-Kincaid readability scores mean, why they matter for web writing, and how to use them to cut through dense text.
There’s a specific kind of frustration that comes from reading something twice and still not knowing what it said. Usually the problem isn’t you — it’s the writing. Long sentences, polysyllabic words stacked on top of each other, passive constructions that bury the verb at the end. The Readability Checker puts a number on this.
What Flesch Reading Ease actually measures
Rudolf Flesch published his readability formula in 1948. The formula does two things: it penalizes long sentences and it penalizes long words (measured in syllables). The output is a score from 0 to 100.
The scale roughly breaks down like this:
- 90–100: Comics, children’s books — very short sentences, simple words
- 70–80: Consumer instructions, news briefs — plain English
- 60–70: Standard newspaper prose, most web articles
- 50–60: Professional and technical writing
- 30–50: Academic papers
- Below 30: Legal and scientific journals
A score of 65 is a reasonable target for web content. It’s not dumbed down — it’s readable.
What the Flesch-Kincaid grade level tells you
The grade level formula takes the same inputs (sentence length, syllables per word) and maps them to US school grades. A score of 8 means an eighth grader can follow your text. Most general-audience websites land between 6 and 10.
The grade level is useful when you know your audience. Medical consent forms are legally required to be at an 8th grade reading level in several US states — because that’s the adult literacy baseline. If you’re writing for a general audience and your grade level is 14, you’ve written a college thesis, not a help article.
Why shorter sentences move the needle more than shorter words
Both factors matter, but sentence length typically has more leverage. Cutting a 35-word sentence into two 17-word sentences improves your Flesch score faster than swapping “utilize” for “use.” That said, syllable count isn’t irrelevant — a paragraph full of “implementation,” “documentation,” and “configuration” will drag the score down even if the sentences are short.
A useful practice: after drafting, look for any sentence over 25 words. Most of them can be split without losing meaning.
The limits of the score
Flesch scores measure surface features of writing, not comprehension. A text can score 75 and still be confusing because the ideas are poorly organized. A technical manual for experts might score 35 and be perfectly clear to its intended readers.
The score is a flag, not a verdict. If your article about machine learning scores 40, that’s expected — the vocabulary is necessarily technical. If your onboarding email scores 40, something’s wrong with the sentences.
The formula also only works for English. The syllable counting is tuned to English phonology. Running Russian or French text through it produces numbers that aren’t meaningful.
How to actually improve readability
Split long sentences at conjunctions. “The report describes the findings and also includes recommendations for future research” becomes two sentences. Better.
Replace weak verbs and their nouns with strong verbs. “Make a decision” → “decide.” “Provide assistance” → “help.” “Conduct an investigation” → “investigate.”
Move the main verb earlier. Readers hold the subject in their head while waiting for the verb. The longer they wait, the harder the sentence feels.
Cut qualifiers that add no information. “Very unique” → “unique.” “Completely finished” → “finished.” “Currently ongoing” → “ongoing.”
Paste any piece of writing into the Readability Checker and you’ll see the Flesch score, grade level, average sentence length, and syllable count update instantly. No signup, no upload — everything runs in your browser.