Readability Checker

How to Use the Readability Checker

1. Paste or type any passage into the input area — a blog draft, a product description, an email, an academic abstract, or a piece of marketing copy.
2. The headline Flesch Reading Ease score updates instantly, alongside a plain-English label and the target audience for that reading level.
3. Compare the grade-level scores below — Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, and ARI each provide a slightly different lens.
4. Edit the text in place. Shorter sentences and simpler words push the score up. Scores recompute on every keystroke.
5. Click Copy text when you are happy with the result, or Load sample to see how the metrics look on a benchmark paragraph.

Understanding the Flesch Reading Ease Score

Flesch Reading Ease maps any passage to a 0–100 scale where higher means easier to read. It is the most cited readability score in publishing, education, and US federal plain-language guidelines. The formula uses two inputs only — average sentence length and average syllables per word — which makes it fast to compute and stable across topics.

The Six Readability Formulas Explained

• Flesch Reading Ease — 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). Higher is easier. Best for general writing.
• Flesch-Kincaid Grade Level — Re-expresses the same inputs as a US school grade. Used by the US Department of Defense for technical documentation.
• Gunning Fog Index — 0.4 × (avg sentence length + 100 × complex-word ratio). "Complex" means three or more syllables. Favoured for business writing.
• SMOG (Simple Measure of Gobbledygook) — 1.0430 × √(complex words × 30 ÷ sentences) + 3.1291. Recommended by the US National Cancer Institute for health materials. Most reliable with 30+ sentences of input.
• Coleman-Liau Index — 0.0588 × L − 0.296 × S − 15.8 (where L is letters per 100 words and S is sentences per 100 words). Uses character counts rather than syllables — robust on text with unusual words.
• Automated Readability Index (ARI) — 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43. Originally designed for US Army training manuals; another character-based formula.

How Syllables Are Counted

Syllables are estimated client-side with a standard vowel-group heuristic. Each word is lowercased, non-letters are stripped, a silent trailing e (or es, ed) is removed, and the remaining vowel runs (a, e, i, o, u, y) are counted as one syllable each. Every word is clamped to at least one syllable. This is the same approach used by most popular readability tools — accurate enough for the Flesch family of formulas without needing a full pronunciation dictionary.

When to Use This Tool

• Web copy and blog posts — aim for Flesch 60–70 (Grade 8–9) so search engines and casual readers stay engaged.
• Marketing emails and landing pages — push for 70–80 to maximise conversions on a mixed audience.
• Healthcare and public information — the CDC and NHS recommend Grade 6–8 (Flesch 70+). Use SMOG with at least 30 sentences for the most defensible score.
• Technical documentation — 30–50 is acceptable for a specialist audience, but watch for sentences over 25 words — those almost always lower the score.
• Academic writing — readability scores are not a substitute for editorial judgement, but a sudden drop into the 20s usually signals overlong sentences or unnecessary jargon.
• Plain-language compliance — US Plain Writing Act (2010) and EU plain-language guidelines reference these formulas for government-facing content.

Tips for Lifting a Low Score

• Break sentences longer than 20–25 words into two.
• Replace polysyllabic words (utilise → use, demonstrate → show, approximately → about).
• Cut filler phrases ("in order to", "due to the fact that", "at this point in time").
• Use the active voice — passive constructions usually add words and syllables.
• Front-load the key idea so readers don't have to parse a clause before the meaning lands.