What is the Flesch Reading Ease score?

The Flesch Reading Ease formula produces a score from 0 to 100. Higher scores mean easier reading. A score of 60-70 is considered plain English suitable for a general audience. Scores below 30 are very academic or technical. The formula penalises long sentences and long words (measured in syllables).

What does the Gunning Fog Index measure?

The Gunning Fog Index estimates the years of formal education a reader needs to understand the text on the first reading. It counts the percentage of complex words — those with three or more syllables — and the average sentence length. A score of 12 corresponds to US high-school level; scores above 17 are considered difficult for most readers.

How is syllable count calculated?

The tool uses a heuristic algorithm that counts vowel groups in each word, with adjustments for common silent-e patterns, diphthongs, and short words. It is accurate for most standard English text but may differ slightly from a manual count for unusual or technical words.

Which formula should I trust most?

No single formula is definitive. Flesch Reading Ease and Flesch-Kincaid Grade Level are the most widely used and cited. Gunning Fog is popular in journalism. SMOG is often preferred for health and medical documents. Coleman-Liau relies on character counts rather than syllables, making it more consistent for digital text. Looking at the consensus across all five gives the best picture.

Reading Level Checker

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The Reading Level Checker calculates five industry-standard readability formulas on any text you paste in, giving you a comprehensive picture of how easy or difficult your writing is to understand. Flesch Reading Ease scores from 0 (very difficult) to 100 (very easy). Flesch-Kincaid Grade Level, Gunning Fog Index, SMOG Index, and Coleman-Liau Index each output an approximate US school grade level. The tool also shows word count, sentence count, syllable count, average words per sentence, and average syllables per word — the raw numbers behind the formulas. Each score is accompanied by a plain-English difficulty label (Very Easy, Easy, Fairly Easy, Standard, Fairly Difficult, Difficult, Very Confusing) and an estimated reader age range. Ideal for writers, educators, content marketers, and UX researchers.

Cómo usar

1 Paste your text into the input area.
2 Scores and counts update automatically as you type or paste.
3 Check the Flesch Reading Ease gauge for an overall difficulty rating.
4 Read the grade level estimates from each of the five formulas.
5 Use the difficulty label and age range to gauge your audience fit.
6 Edit your text to shorter sentences or simpler words to improve the scores.

What a readability score really measures

Readability formulas do not judge whether your ideas are good — they estimate how much mental effort a reader needs to decode your sentences. Almost all of them rest on two surprisingly powerful signals: how long your sentences are and how long your words are. Long sentences strain working memory because the reader has to hold more in mind before reaching a full stop. Long words (measured in syllables or letters) are more often rare, abstract, or technical. Combine those two measures with the right constants and you get a number that tracks reading difficulty remarkably well. This tool runs five established formulas on your text at once, because no single one is authoritative and the spread between them is itself informative.

The five formulas and their exact inputs

Each formula weighs the same raw counts differently. Here is what this tool actually computes:

Formula	Output	Driven by
Flesch Reading Ease	0–100 (higher = easier)	Words/sentence and syllables/word
Flesch–Kincaid Grade	US school grade	Words/sentence and syllables/word
Gunning Fog Index	Years of education	Sentence length and % of 3+ syllable words
SMOG Index	US school grade	Count of 3+ syllable words
Coleman–Liau Index	US school grade	Letters per word and sentences per 100 words

The Flesch Reading Ease score uses the classic equation 206.835 − 1.015 × (words/sentence) − 84.6 × (syllables/word). Notice the two penalties: each extra word per sentence costs about a point, and each extra syllable per word costs nearly 85 points, which is why long words punish your score far harder than long sentences. Coleman–Liau is the odd one out: it counts letters rather than syllables, which makes it more consistent for digital text where syllable estimation is fuzzy. The tool also averages the four grade-level formulas into a single "consensus" grade so you have one headline number.

A worked example

Take the sentence "The cat sat on the warm mat." That is 7 words in 1 sentence, so words-per-sentence is 7. Every word is one syllable, so syllables-per-word is 1.0. Plug those into Flesch Reading Ease: 206.835 − 1.015 × 7 − 84.6 × 1.0 ≈ 115, which the tool caps and labels "Very Easy." Now rewrite it as "The feline reclined upon the heated rectangular textile." Same single sentence, but 8 words and roughly 16 syllables, so syllables-per-word jumps to about 2.0. The score collapses toward 35 — "Difficult." Nothing about the meaning changed; only the word and sentence lengths did, and the formulas felt every bit of it.

How the syllable counter works (and where it slips)

Syllables are the hard part, because English spelling is irregular. This tool uses a heuristic rather than a dictionary: words of three letters or fewer count as one syllable, common silent endings like -es, -ed, and a trailing silent e are stripped, a leading y is ignored, and then it counts the remaining vowel groups (runs of a, e, i, o, u, y). For ordinary prose this is accurate, but it will miscount unusual or technical words — "queue," compound coinages, and many proper nouns trip it up. That is normal for every fast readability checker; if your text is dense with jargon, treat the grades as approximate.

Who uses this and why

Content writers and marketers aim for a Flesch Reading Ease around 60–70 — plain English a general web audience reads comfortably.
Teachers match a passage's grade level to their students' age before assigning it.
Health and government communicators often target grade 6–8 so critical instructions are understood by the widest possible audience; SMOG is the traditional favourite for medical material.
UX writers check that error messages, onboarding, and microcopy stay low-effort under stress.

Practical tips to improve a score

Split long sentences. Because sentence length feeds every formula, breaking one 30-word sentence into two 15-word ones is the fastest single improvement.
Swap long words for short ones. "Use" beats "utilise," "help" beats "facilitate." Each multi-syllable word you remove lifts the Flesch score and lowers the grade.
Do not over-optimise. A score above 90 can read as choppy and patronising. Aim for the band that fits your audience, not the maximum.
Read the consensus, not one number. If four formulas agree and one is an outlier, trust the cluster. A wide spread usually means very short text or unusual vocabulary skewing a single formula.

One caveat about short text

Readability formulas were designed for paragraphs, not fragments. SMOG in particular was calibrated for samples of about 30 sentences and falls back to a rougher estimate below that. The analysis here needs at least one complete sentence to produce scores, but the more text you paste, the more stable and trustworthy the numbers become. For a fair reading, feed it a few hundred words rather than a single line.