Readability Score Checker
Check text readability with Flesch-Kincaid, Gunning Fog, and SMOG scores. Free readability analyzer - improve your writing.
Three steps to get started
Paste your text
Type or paste any text - articles, essays, emails, blog posts, or academic papers.
View scores and highlights
See Flesch-Kincaid, Gunning Fog, and SMOG scores update instantly, with hard sentences, adverbs, passive phrases, and complex words highlighted right in your text.
Improve your writing
Split the highlighted hard sentences, trim adverbs and passive phrases, and swap complex words for their simpler alternatives to reach a wider audience.
Why readability scores matter
A readability formula is an arithmetic model that estimates how hard a text is to read from two surface features: sentence length and word length. None of them evaluate logic, structure, or whether the writing is any good - they measure syntactic and lexical load, and that proxy turns out to correlate well enough with comprehension to be useful. This tool computes three of the most established ones live as you type.
Flesch–Kincaid Grade Level, published by J. Peter Kincaid for the US Navy in 1975, maps a text onto a US school grade. The formula is0.39 × (words / sentences) + 11.8 × (syllables / words) − 15.59. A score of 8 means an average eighth-grader can read it. It is the grade-level companion to the older Flesch Reading Ease score embedded in Microsoft Word's spelling and grammar panel; this tool reports grade levels rather than the 0–100 ease scale, because grade levels are directly comparable across all three formulas below.
Gunning Fog Index, devised by publisher Robert Gunning in 1952 for business writing, is 0.4 × [(words / sentences) + 100 × (complex words / words)], where complex words are those of three or more syllables. It returns years of formal education needed for first-reading comprehension. Newspapers typically land at 11–12; Reader's Digest around 9. SMOG - Simple Measure of Gobbledygook, G. Harry McLaughlin, 1969 - is 3 + √(complex words × 30 / sentences), the square root of the polysyllable count normalised to a 30-sentence sample. It has the highest reported validity of the three (roughly 0.985 correlation on its validation set), which is why healthcare and government plain-language programs specify it.
What score should you aim for?
- Consumer web and marketing copy - grade 6–8; the average US adult reads at roughly grade 8
- News and general blogging - grade 8–10, matching most national newspapers
- Patient information and government forms - grade 6 or below; the CDC recommends grade 8 maximum, and many state plain-language statutes set a comparable ceiling
- B2B and technical documentation - grade 10–12 is acceptable when the audience is specialist
- Academic papers - grade 14+ is normal and not a defect
Two caveats keep you from gaming the number. First, these formulas areblind to meaning: "Cat sat mat. Dog ran log." scores at grade 1 while saying nothing, and a paragraph of short sentences full of undefined jargon can score better than clear prose containing the word "particularly". Second,SMOG needs volume - it was designed on 30-sentence samples, so a three-sentence excerpt gives an unreliable figure. Expect SMOG to read one to two grades above Flesch–Kincaid on the same text; that gap is inherent to the formulas, not an error.
To move the numbers meaningfully rather than cosmetically: split sentences that run past about 20 words, replace Latinate multisyllables with Anglo-Saxon equivalents ("use" for "utilize", "help" for "facilitate"), convert passive constructions to active, and define a technical term once instead of paraphrasing around it. Everything is calculated in JavaScript inside this page as you type - no round trip, and the optional auto-save writes only to your own browser's localStorage.