Readability Checker
Calculate Flesch-Kincaid Grade, Flesch Reading Ease, Gunning Fog, SMOG, Coleman-Liau, and ARI scores instantly. See exactly how complex your writing is.
Free Online Readability Checker
Our Readability Checker calculates six standard readability scores in real time: Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau, and the Automated Readability Index (ARI). Paste any text and instantly see how easy or difficult it is to read.
Why Readability Matters
Most online content is targeted at an 8th-grade reading level, which corresponds to a Flesch Reading Ease score of around 60-70. Writing too far above your audience's reading level reduces comprehension, engagement, and conversion. Newspapers, blogs, and marketing copy benefit from clear, plain language.
Different formulas use different inputs. Flesch and SMOG rely on syllable counts, while Coleman-Liau and ARI use only character counts. Comparing all six gives a more reliable picture than any single score. Aim for a tight range across all five grade-level scores: that means your text reads consistently.
What Are Readability Scores?
Readability scores are formulas that estimate how easy or hard a piece of text is to read. They look at surface features such as sentence length, word length, and syllable count, then translate those into a grade level or an ease score. The goal is to match writing to its audience: a children's book should read at a 3rd grade level, a marketing email at around 8th grade, and a research paper at 14th grade or higher.
These formulas exist because comprehension drops fast when writing outpaces a reader's ability. Studies of newspapers, textbooks, and government documents show that readers skim or abandon text that scores more than 2 grades above their reading level. Even highly educated audiences prefer simpler writing when they can get it. Running your draft through a readability checker is a quick way to spot sentences that are too long, words that are too dense, or sections that drift above your target audience.
The 6 Formulas Explained
Flesch Reading Ease scores text on a 0 to 100 scale, where higher means easier. A score of 60 to 70 is considered standard for adult readers. The formula uses two inputs: average sentence length and average syllables per word. Long sentences and dense, multi-syllable words drive the score down.
Flesch-Kincaid Grade Level takes the same two inputs as Flesch Reading Ease (sentence length and syllable density) but rescales them into a US grade level. A score of 8.0 means an average 8th grader can understand the text on a first reading. It is the most widely used readability measure in education and government.
Gunning Fog Index estimates the years of formal education a reader needs to understand the text on a first reading. Instead of counting syllables, it counts "complex words" defined as words with 3 or more syllables. The formula combines this with average sentence length, so a fog index of 12 means the text is suitable for a 12th grader.
SMOG (Simple Measure of Gobbledygook) is the most accurate formula for texts of at least 30 sentences. It counts polysyllabic words (3 or more syllables) and converts that count into a grade-level estimate. SMOG is the standard formula used in healthcare for evaluating patient education materials.
Coleman-Liau Index outputs a US grade level using character count rather than syllables. Because counting characters is more reliable than counting syllables (especially for unusual words and non-standard text), Coleman-Liau is useful for technical documents, code-adjacent writing, and any text where syllable detection would struggle.
Automated Readability Index (ARI) uses the same character-count approach as Coleman-Liau and produces a US grade level. It was originally designed for real-time analysis on early electric typewriters, where character count was easy to capture. Today it remains a solid sanity check that does not depend on syllable estimation.
Which Score Should I Trust?
No single formula is perfect. Each has blind spots: Flesch-Kincaid can be fooled by short sentences with many simple syllables, Gunning Fog penalizes technical vocabulary even when it is necessary, and SMOG needs a large sample to be stable. The most robust approach is to average the 5 grade-level scores (Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, ARI) for a reliable estimate of where your text sits.
Flesch Reading Ease lives on a different scale (0 to 100), so do not average it with the others. Use it as a separate audience-match check: if it lands in the 60 to 70 band, your text is in the standard adult range. If it drops below 50, you are writing at a college level whether you meant to or not.
Recommended Reading Levels by Audience
Match your writing to the audience you actually have, not the one you wish you had. These are typical targets:
| Audience | Grade Level | Flesch Reading Ease |
|---|---|---|
| General public | 6th to 8th | 60 to 70 (Standard) |
| Marketing / SEO content | 7th to 9th | 55 to 65 |
| News articles (NYT / WaPo) | 9th to 12th | 45 to 60 |
| Academic papers | 13+ (graduate) | 30 to 45 |
| Legal documents | 13 to 17 | 10 to 30 |
| Children's content | 3rd to 5th | 80+ (Easy) |
How to Improve Readability
If your scores come back too high for your audience, the fixes are predictable and effective:
- Shorten sentences. Aim for an average of 15 to 20 words. Break any sentence over 25 words into two.
- Use simpler words. Swap 3+ syllable words for shorter alternatives when possible (use "help" instead of "facilitate", "show" instead of "demonstrate").
- Prefer active voice. "The team shipped the feature" reads cleaner than "The feature was shipped by the team" and uses fewer words.
- Add bullet points and lists. Lists break up dense prose, give the eye a place to rest, and force you to compress each idea.
- Use headers and subheadings. Headers signal structure, let readers scan, and break long sections into digestible chunks.
Apply these one at a time and re-run the checker. You will usually see a 1 to 2 grade-level drop after a single careful editing pass.
A Flesch Reading Ease score between 60 and 70 is considered standard and easy for most adult readers to follow. Scores of 80 to 100 are very easy and suit children's content or wide consumer audiences. Scores below 50 are considered difficult, and scores under 30 read at a college graduate level. For general web content, marketing copy, and blog posts, aim for 60 to 70.
For general public content, aim for 6th to 8th grade level. Marketing and SEO content reads best at 7th to 9th grade. News articles like the New York Times sit around 9th to 12th grade. Academic papers run 13 and up (graduate level), and legal documents often reach 13 to 17. Children's content should target 3rd to 5th grade. Lower is almost always better for engagement and comprehension.
Each formula uses different inputs and weighting. Flesch and Flesch-Kincaid count syllables per word and words per sentence. Gunning Fog and SMOG count complex or polysyllabic words. Coleman-Liau and ARI use character counts instead of syllables. Because the inputs differ, you can see grade-level estimates that vary by 1 to 3 grades for the same text. Averaging the grade-level scores gives the most reliable estimate.
The formulas were designed and calibrated for English text. They will produce numbers for other languages, but the results are not meaningful since syllable patterns, average word length, and sentence structure differ across languages. For Spanish, look at the Fernandez Huerta or Szigriszt-Pazos formulas. For German, the Wiener Sachtextformel is the standard.
Yes, but expect higher grade-level scores. Academic writing typically reads at 13 to 17 grade level due to specialized vocabulary, longer sentences, and necessary precision. Use the tool to spot sentences that are needlessly complex rather than to chase a low number. A research paper that drops below 12th grade is probably losing technical accuracy.
In the Gunning Fog formula, a "complex word" is any word with three or more syllables, excluding proper nouns, common suffixes like "-es" and "-ed", and compound words made of simpler parts. The formula counts the percentage of complex words in your text and combines that with average sentence length to estimate the years of education needed to understand the writing on a first reading.
SMOG (Simple Measure of Gobbledygook) was statistically calibrated on samples of 30 sentences (10 from the start, 10 from the middle, 10 from the end). The formula assumes a sample of that size to produce its grade-level estimate. With fewer sentences, the polysyllable count becomes too noisy and the grade level can swing wildly. For texts under 30 sentences, trust the other 5 formulas more.
Readability formulas are useful proxies, not precise measurements. They count surface features like sentence length and syllable density but cannot judge whether ideas are clearly organized, whether transitions flow, or whether vocabulary fits the audience. Use them as a sanity check: if your text scores at grade 16 and your audience is the general public, you have a problem. But a grade 8 score does not guarantee good writing.
Related Guides
Readability Scores Explained: Flesch, Gunning Fog, SMOG
How each readability formula works, what scores mean, and how to choose targets for your audience.
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