What This Tool Does
Paste any English text and get four standard readability scores calculated instantly. The scores tell you which US school grade level a reader needs to comfortably understand your writing, and how much effort your average sentence and word complexity demands. No assumptions about your text — the formulas run in your browser on the exact words you provide.
The Four Formulas Explained
- Flesch Reading Ease — A score from 0 to 100. Higher is easier. Scores above 60 are generally readable for most adults. Scores below 30 are considered difficult, typical of academic or legal writing.
- Flesch-Kincaid Grade Level — Converts the Flesch formula into a US school grade (Grade 5 = fifth grade, Grade 12 = senior year of high school). Most general-audience content targets Grade 7–9.
- Gunning Fog Index — Estimates grade level based on average sentence length and the percentage of complex words (three or more syllables). A score of 12 is readable for a high-school senior; over 17 is considered college-graduate level.
- SMOG Grade — Simple Measure of Gobbledygook. Focuses entirely on polysyllabic words. Generally considered accurate for healthcare communications and patient education materials. Needs at least 3 sentences for a valid result.
Target Scores by Audience
- General public / consumer: Flesch 60–70, Kincaid Grade 7–9
- Business and marketing: Flesch 50–70, Kincaid Grade 9–11
- Journalism and news: Flesch 65+, Kincaid Grade 8 or below
- Academic papers: Flesch 20–40, Kincaid Grade 14–18
- Legal documents: Flesch 10–30 (but aim for higher if you can)
Frequently Asked Questions
How accurate are readability formulas?
Readability formulas measure surface features — sentence length and word complexity — not actual comprehension. They are useful directional signals, not precise guarantees. A text can have a good score but still be confusing if it uses unfamiliar jargon or poorly organized ideas.
Why does SMOG show a dash sometimes?
SMOG requires at least 3 sentences to produce a valid result. With fewer sentences, the formula is not reliable, so the tool shows a dash rather than a misleading number. For best SMOG results, the formula was originally designed for 30-sentence samples.
What counts as a complex word?
Complex words (also called polysyllabic words) have three or more syllables. Words like understanding (4 syllables) or communication (5 syllables) count as complex. Words like book or simple do not.
Which formula should I trust most?
Flesch Reading Ease is the most widely used and studied. Flesch-Kincaid is standard in US education. Gunning Fog is popular for business writing. Looking at all four together gives a more reliable picture than relying on any single score.
Is my text sent to a server?
No. All formulas run in your browser. Nothing is uploaded.