Analyse your text with 6 readability formulas simultaneously — Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG Index, Coleman-Liau, and ARI. Get a consensus grade level, plain-English audience label, and writing improvement tips.
Paste any content — a blog post, product description, email, landing page copy, academic paper, or marketing material. For reliable results, use at least 100 words. The tool calculates all six scores simultaneously as soon as text is present.
See Flesch Reading Ease (0–100 scale), Flesch-Kincaid Grade Level (US school grade), Gunning Fog Index (years of education needed), SMOG Index (polysyllabic word focus), Coleman-Liau Index (character-based), and Automated Readability Index (ARI). Each score is colour-coded — green for easy, amber for moderate, red for difficult.
The Consensus Grade is the average of all six grade-level scores, which is more reliable than any single formula alone. The plain-English audience label tells you who can read your text (e.g. "General public", "High school student", "College graduate"). The tips panel flags the most impactful improvements: sentences over 20 words, words with 3+ syllables, and average syllables per word.
Flesch Reading Ease is a 0–100 score where higher is easier. The formula is 206.835 − 1.015 × (words/sentences) − 84.6 × (syllables/words). Scores: 90–100 = very easy (understood by a 10-year-old); 70–80 = easy (understood by a 13-year-old); 60–70 = standard (plain English); 50–60 = fairly difficult (high school level); 30–50 = difficult (college level); 0–30 = very difficult (academic/professional). US government guidelines recommend a score above 60 for public communications.
Both output a US grade level, but they measure different things. Flesch-Kincaid Grade (0.39 × words/sentences + 11.8 × syllables/words − 15.59) weights syllable count and sentence length equally. Gunning Fog (0.4 × (words/sentences + 100 × complexWords/words)) weights complex words — those with 3+ syllables — much more heavily. Fog is more sensitive to jargon. A text with many short sentences but heavy technical vocabulary will score higher on Fog than FK. Using both together gives a more complete picture.
SMOG (Simple Measure of Gobbledygook) is designed specifically to estimate the years of education needed to comprehend a text. It focuses exclusively on polysyllabic words (3+ syllables): SMOG Grade = 3 + √(polysyllabic word count × 30/sentence count). SMOG is considered more accurate than other formulas for health literacy materials and is recommended by the US National Institutes of Health for patient education documents. It requires at least 30 sentences for reliable results.
The Coleman-Liau Index is unique because it avoids syllable counting entirely, using character counts instead: CLI = 0.0588 × (letters per 100 words) − 0.296 × (sentences per 100 words) − 15.8. This makes it more consistent across different text types, particularly for texts with many short technical abbreviations. It tends to be more reliable than syllable-based formulas for technical and scientific writing.
It depends entirely on your audience. Plain language guidelines for government and healthcare: aim for Flesch 60+ (Grade 8 or below). Blog posts and general web content: Flesch 60–70 (Grade 7–9). B2B marketing and business writing: Flesch 50–60 (Grade 10–12). Academic papers: Flesch 30–50 (College level) is expected and appropriate. Children's content: Flesch 80+ (Grade 4 or below). The key principle is to write at the lowest level your audience can accept without feeling patronised.
Each formula weighs different factors and was calibrated on different text samples. Disagreement between formulas is normal and informative. A wide spread (more than 4 grade levels between lowest and highest) often signals inconsistent writing — some sections are dense and some are very simple. The Consensus Grade averages all six to reduce the noise from any single formula's quirks. Use the individual scores to understand where the variation is coming from.
