π Readability Checker
Flesch, Gunning Fog, SMOG, and Coleman-Liau scores instantly.
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Everything runs in your browser. Your text never leaves your device.
How to Use This Tool
Paste any text and the tool scores it with five established readability formulas, counts words, sentences, and syllables, and highlights the longest sentences so you know exactly what to rewrite.
Paste your text: a blog draft, essay, product description, or email. At least 100 words gives the most stable scores.
Read the Flesch Reading Ease score and verdict first: 60 to 70 is plain English, the target for most web content.
Check the grade-level scores (Flesch-Kincaid, Fog, SMOG, Coleman-Liau). For blogs, aim for grade 8 or below.
Rewrite the highlighted long sentences: split them, shorten words, and re-run until the scores land in range.
The Formulas
Every formula here combines sentence length with word complexity, because those two factors explain most of reading difficulty. Flesch counts syllables per word; Coleman-Liau uses letters per word instead, which makes it steadier on short texts. Gunning Fog and SMOG single out polysyllabic words (3+ syllables) as the complexity signal. Syllables are counted with a vowel-group heuristic: groups of adjacent vowels count as one syllable, a silent trailing "e" is subtracted, and a consonant-plus-"le" ending (like "table") adds one back. It matches dictionary counts about 90 percent of the time, close enough for scoring.
Worked Example
Text: "The cat sat on the mat. It was a hot day." Words: 11. Sentences: 2. Syllables: 11 (every word is one syllable). Flesch Reading Ease = 206.835 - 1.015 x (11/2) - 84.6 x (11/11) = 206.835 - 5.58 - 84.6 = 116.7, capped at 100: extremely easy. Flesch-Kincaid Grade = 0.39 x 5.5 + 11.8 x 1 - 15.59 = 2.15 + 11.8 - 15.59 = -1.6, floored near grade 0. Now the opposite: a 45-word sentence packed with "utilization", "implementation", and "characterization" scores a Reading Ease near 10 and a grade above 16. Same information, rewritten into three short sentences with plain words, typically lands around grade 8.
Before and After Rewriting
Before: "The utilization of comprehensive methodologies for the implementation of search engine optimization strategies necessitates considerable characterization of target demographics." (Grade 16+, Fog 18.) After: "Good SEO starts with knowing your audience. Pick clear methods, apply them consistently, and measure what happens." (Grade 7, Fog 8.) The rewrite rule is mechanical: cut average sentence length under 20 words, replace 3+ syllable words with 1 to 2 syllable ones where the meaning survives, and prefer active voice. Run both versions through the checker and compare: the score delta tells you whether the edit actually helped or just felt better. Writers who check readability before every publish ship consistently clearer content, and clearer content keeps readers on the page. Your text never leaves your browser.
Frequently Asked Questions
What is a good Flesch-Kincaid grade for blog posts?
Grade 7 to 9 is the sweet spot for general web content: readable by most adults without feeling dumbed down. News sites typically land at grade 8 to 10, marketing copy at 6 to 8. Academic papers often score grade 14+, which is fine for journals but deadly for blogs. If your post scores above grade 10, shorten sentences and swap long words for short ones before publishing.
What is the difference between Reading Ease and Grade Level?
Flesch Reading Ease scores 0 to 100, where higher is easier (60 to 70 is plain English). Flesch-Kincaid Grade Level converts the same inputs into a US school grade (8.0 means an eighth grader can read it). They use the same word, sentence, and syllable counts in different formulas. Use Reading Ease for a quick feel and Grade Level when you need a concrete target to hit.
How do I make my text more readable?
Three levers move the score most: shorter sentences (aim for 15 to 20 words average), shorter words (prefer "use" over "utilize"), and fewer clauses per sentence. Break one 40-word sentence into two 20-word ones and watch the grade drop two levels. Active voice, concrete nouns, and deleting filler phrases ("in order to", "due to the fact that") help too. This tool highlights your longest sentences so you know exactly where to cut.
What is the Gunning Fog index?
An alternative readability formula: 0.4 times (average sentence length plus the percentage of complex words, where complex means 3 or more syllables). It estimates the years of education needed to understand the text. A Fog index of 8 to 10 suits general audiences; above 12 feels academic. It punishes long sentences and jargon-heavy vocabulary harder than Flesch does, which makes it useful for business and technical writing.
Does readability affect SEO?
Indirectly but really. Google does not use Flesch scores as a direct ranking factor, but readable pages earn longer dwell time, lower bounce rates, and more shares and links, all of which correlate with rankings. Google's own guidelines reward content written for people, and people bounce from walls of dense text. Aim for grade 8 or below on money pages and blog posts; your readers and your metrics will thank you.