Reading Level Calculator

About this tool

Flesch, FK, Fog, SMOG, CL, ARI

Paste any text to compute 6 readability scores — Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau, ARI — plus long-sentence flags and plain-English suggestions.

RT-TXT-051 · Text Tools

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Flesch Reading Ease

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— 0-100 · higher = easier

60-70 = standard 8th-9th grade · the most quoted readability number

Flesch-Kincaid Grade

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US school grade

Used by US government plain-language requirements (DoD MIL-STD-1689A origin)

Gunning Fog Index

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Years of education needed

Robert Gunning, 1952 — weights long sentences and complex words

SMOG Index

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Years for 100% comprehension

Harry McLaughlin, 1969 — "Simple Measure Of Gobbledygook" · health-comms standard

Coleman-Liau

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US grade level

Uses characters not syllables — easier to compute mechanically (1975)

Automated Readability Index

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US grade level

Smith & Senter, 1967 — designed for typewriter / electric output

Long sentences (> 25 words)

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Plain-English suggestions

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How to use the Reading Level Calculator

Paste your text into the box

Drop in an article, blog post, marketing email, product description, or contract. The tool starts with a Hemingway sample text already loaded so you can see how the scores look immediately. All processing runs in your browser — nothing is sent to a server. For statistically reliable scores, paste at least 100 words; ideally 200 or more. Short blocks (under 30 words) are directional only — formulas were calibrated on much larger samples.

Read the six scores together, not in isolation

Flesch Reading Ease is the headline number (0–100, higher is easier). The five grade-level formulas (FK, Fog, SMOG, Coleman-Liau, ARI) cluster around the same answer using different inputs — sentence length, syllable count, character count. If they all agree at grade 8, the answer is grade 8. If they spread widely (e.g. FK says grade 10 but SMOG says grade 14), the text has unusual properties (lots of polysyllabic words crammed into short sentences, or vice versa) and the higher number is usually the more honest one.

Act on the long-sentence and substitution panels

The right-hand panels are the practical part. Long sentences (over 25 words) are by far the biggest single cause of high grade-level scores — breaking a 40-word sentence into two 20-word sentences drops the score immediately. The substitution panel flags common bureaucratic words with plain-English alternatives: utilise → use, commence → start, terminate → end, facilitate → help, demonstrate → show. Most "professional" writing scores 2–4 grade levels too high primarily for these two reasons.

Edit and re-paste — aim for grade 8 unless your audience is expert

The US government plain-language standard, the UK gov.uk style guide, and most newsroom style guides target grade 6–8. High-conversion marketing copy typically lands around grade 5–7. B2B technical content can sit at grade 10–12. Reserve grade 14+ for peer-reviewed papers, legal documents, and audiences you genuinely know are college-educated specialists. Edit, paste back in, and watch the score move. The feedback loop is the entire value of the tool.

Readability formulas, plain English, and the cost of writing above your audience

Readability formulas are one of the oldest applications of statistics to language. The earliest serious effort was Lively and Pressey in 1923, who counted hard-word frequency in school textbooks. By the late 1940s Rudolf Flesch had codified what is now known as the Flesch Reading Ease score — a single number from 0 to 100 that estimates how hard a passage is to read, with higher meaning easier. Flesch's score was so influential that the US Department of Defense, the IRS, the state of Florida (which legally requires insurance policies to score at least 45 on Flesch), and most state-government plain-language guidelines still reference it directly. The Flesch-Kincaid Grade Level (a 1975 reformulation by J. Peter Kincaid for the US Navy) is built into Microsoft Word, Google Docs, and most newsroom CMSs — every word processor on your desk computes it whether you've asked it to or not.

What each formula actually measures — and where they disagree

The six formulas in this tool measure different combinations of sentence length and word complexity. Flesch Reading Ease is the most quoted because the scale is intuitive: 60–70 is standard 8th–9th grade reading; 90+ is children's books; below 30 is academic prose. Flesch-Kincaid Grade Level converts the same input into a US school grade — so "grade 8" means a US 8th-grader (roughly 13–14 years old) can comfortably read it. Gunning Fog (Robert Gunning, 1952) weights complex words (3+ syllables) heavily and is popular in business and journalism. SMOG (Harry McLaughlin, 1969 — yes, it stands for "Simple Measure Of Gobbledygook") is the standard in healthcare communication because it estimates the grade level for 100% comprehension rather than partial comprehension. Coleman-Liau (1975) and ARI (1967) avoid counting syllables — they use character counts instead, which makes them more accurate for machine processing and less sensitive to the syllable-counter's approximations. When all six broadly agree, you can trust the answer; when they spread, the higher number is usually the right one to act on.

Most professional writing scores at grade 14–16 — college / graduate level. The same content rewritten at grade 8 reaches 3× the audience without losing precision. Plain English is a competitive advantage.

Why "grade 8" is the universal target

The US Department of Education estimates that the average American adult reads at roughly an 8th-grade level. The UK Office for National Statistics finds the equivalent for British adults is similar. The numbers are even starker once you account for adults whose first language isn't English — the US has 67 million such adults, the UK around 8 million, and across ASEAN the figure is well over 200 million who speak English as a second language. When a piece of writing scores at grade 14 (college sophomore), comprehension among general adult readers falls below 50%. At grade 16 (college graduate), it drops below 30%. Every grade level above 8 you climb, you lose roughly 10% of your potential audience — not because they aren't smart, but because dense prose requires re-reading, and re-reading requires motivation the reader rarely has on the open web. Plain English isn't dumbing down. It's removing friction.

The two highest-leverage fixes — sentence length and word substitution

The fastest way to drop your grade level is to shorten sentences. A 35-word sentence almost always contains two ideas; splitting it into two 15–17 word sentences usually drops the score by a full grade level without changing the meaning. The second-fastest is plain-word substitution. Latinate words (utilise, commence, terminate, facilitate, demonstrate) sound formal but inflate syllable counts, which most formulas weight heavily. Their Anglo-Saxon equivalents (use, start, end, help, show) are usually monosyllabic, score better, and read more directly. George Orwell's six rules from "Politics and the English Language" (1946) still apply: never use a long word where a short one will do; if it is possible to cut a word out, always cut it out; never use the passive where you can use the active; never use a foreign phrase, scientific word, or jargon word if you can think of an everyday English equivalent. Every modern style guide, from the AP Stylebook to the Economist Style Guide, descends from those six rules.

ASEAN context — bilingual writing and the readability blind spot

English-language readability formulas were calibrated on monolingual American and British English text in the mid-20th century. They work well for English written for native English readers. They have structural blind spots for the bilingual and multilingual reality of ASEAN content marketing. Mandarin Chinese, Bahasa Malaysia, Tamil, Thai, and Vietnamese don't map onto these formulas at all — Chinese characters carry the semantic weight of full English words, so character-based counts (Coleman-Liau, ARI) over-penalise CJK text. Use these formulas only for the English-only portions of your text. The practical implication for Singapore, Malaysia, Hong Kong, and Philippines content teams: when writing English for an APAC audience whose first language often isn't English, target grade 6–7, not grade 8 — because the reader is doing the additional cognitive work of translating mentally. Singapore's Straits Times, Malaysia's The Star, and Hong Kong's South China Morning Post have all moved their newsroom style guides toward shorter sentences and plainer vocabulary in the last decade for exactly this reason. Most APAC professional and corporate writing, by contrast, still scores at grade 14–16 — college and graduate level — which means it's quietly losing 50% or more of its potential audience to comprehension friction.

10 Things to Know About Readability

The average US adult reads at roughly an 8th-grade level (US Department of Education). Writing above grade 10 loses roughly 10% of potential audience per grade level climbed.

Rudolf Flesch published the Reading Ease score in 1948. It's so influential that the state of Florida legally requires insurance policies to score at least 45 on Flesch — written into law.

Flesch-Kincaid was commissioned by the US Navy in 1975 (J. Peter Kincaid) to assess Navy training manuals. It's now built into Microsoft Word, Google Docs, and most CMSs by default.

SMOG stands for "Simple Measure Of Gobbledygook" — Harry McLaughlin coined it in 1969 deliberately as a joke that became the formal name of the formula. It's the gold standard in health communication.

Gunning Fog (Robert Gunning, 1952) was invented to measure newspaper and business writing. Time magazine routinely scored Fog 11; the Wall Street Journal scored 11; The New York Times around 11–12.

The US Plain Writing Act of 2010 legally requires every US federal agency to write public-facing documents in plain language — typically defined as Flesch-Kincaid grade 8 or lower.

Coleman-Liau and ARI deliberately avoid syllable counting — they use character counts instead. This makes them more reliable for automated processing because syllable counters always approximate.

George Orwell's "Politics and the English Language" (1946) predates every modern readability formula but still defines the rules: short words, short sentences, active voice, no jargon.

Ernest Hemingway famously wrote at roughly grade 4–5 — his prose scores extremely low on Fog and FK. "The Old Man and the Sea" averages 11.6 words per sentence and is taught as the model of clear English.

The UK gov.uk content design guide targets reading age 9 (grade 4) for all public-facing government text. It's one of the most-cited plain-language guides globally and is freely available online.

Frequently Asked Questions

Look at all six together, not one in isolation. Flesch Reading Ease is the most widely quoted (60–70 = standard 8th–9th grade). Flesch-Kincaid Grade is what Microsoft Word reports. SMOG is the healthcare-industry standard. When all six broadly agree, trust the answer. When they spread by more than 2–3 grade levels, the text has unusual properties (very long sentences with simple words, or very short sentences with academic vocabulary) — and the higher number is usually the more honest one to act on.
Depends on audience. General-public marketing or news: grade 6–8 (Flesch 60–80). B2B / trade publication content: grade 9–12. Academic, scientific, or legal writing: grade 13+. The US Plain Writing Act, UK gov.uk, and most newsroom style guides target grade 6–8. For APAC readers whose first language often isn't English, aim one grade lower than you would for native readers — the reader is doing additional translation work mentally.
Syllable counting uses a standard rule-based approximation: count vowel groups (consecutive vowels = one syllable), subtract silent trailing 'e', adjust for 'le' suffix after a consonant, and clamp the minimum to 1. This is the same approximation used by most open-source readability libraries — it's accurate to within roughly 5% of true syllable count on English text. Words like "the", "and", "is" are clamped to 1 syllable correctly. Edge cases (foreign loanwords, proper names) may misfire slightly, but in aggregate across 100+ words the error averages out.
Because working memory is finite. Cognitive psychology research (Miller's "magical number seven, plus or minus two", 1956; later refined by Cowan to four ±1) shows that adult readers can hold roughly 4–7 chunks of meaning in active memory at once. A 35-word sentence usually contains two or three full ideas — the reader has to hold the first idea while parsing the second, which spikes cognitive load and forces re-reading. Breaking the same 35 words into two 17–18 word sentences keeps each chunk within working-memory limits. Every readability formula models this either directly (words-per-sentence) or indirectly.
No — only English. All six formulas were calibrated on English text and use English syllable patterns. Malay and Bahasa Indonesia use Latin script and roughly map (with caveats around morphology). Mandarin Chinese, Tamil, Thai, and other non-Latin scripts don't map at all — Chinese characters carry the semantic weight of full English words, so character-based formulas (Coleman-Liau, ARI) badly over-penalise CJK text. For multilingual or code-switching content (common in Singapore, Malaysia, Hong Kong), run the tool only against the English portions of your text.
Statistical reliability needs at least 100 words; 200+ is better. Below 30 words, all six formulas are essentially noise — a single long sentence or unusual word can swing the grade level by 3–4 levels. SMOG explicitly was designed for samples of 30 sentences and degrades for shorter passages. For headlines, tweets, or short product descriptions, treat any single-number score as directional only and focus on the long-sentence and substitution panels instead.
Same inputs, different output scale. Both use words-per-sentence and syllables-per-word. Flesch Reading Ease produces a 0–100 score where higher = easier (90+ = very easy, 60–70 = standard, <30 = academic). Flesch-Kincaid Grade Level takes the same inputs and produces a US school grade number directly (8 = US 8th grade, 12 = high school senior, 16 = college graduate). FK Grade is easier to act on; Flesch Ease is easier to compare against industry benchmarks.
No — the opposite. Google's helpful-content guidelines explicitly reward content "written for people first". Lower grade levels correlate with longer dwell time, lower bounce, and higher conversion. Plain English doesn't sound less expert — it sounds more confident. Compare a paragraph by Hemingway (grade 5) to one by a junior consultant trying to sound senior (grade 14); the Hemingway sounds authoritative because every word is doing work. Bureaucratic prose sounds insecure precisely because it hides behind syllables.
"Utilise" has three syllables; "use" has one. Every grade-level formula weights syllables-per-word as a major input, so replacing a 3-syllable word with a 1-syllable synonym drops your grade level immediately. The substitution panel flags a curated list of common Latinate words that have shorter Anglo-Saxon equivalents: utilise → use, commence → start, terminate → end, facilitate → help, demonstrate → show, ascertain → find out, leverage → use, optimise → improve. These swaps don't change meaning — they just reduce friction.
No. All analysis happens entirely in your browser via JavaScript — open DevTools → Network and watch as you type, there is zero outbound traffic. Your text never leaves your device. Fully GDPR and PDPA compliant by design: no personal data collected, nothing stored, nothing logged. When you close the tab, the text is gone.