Paste your content below to get a full readability analysis (Flesch-Kincaid, Gunning Fog, SMOG, ARI), keyword density scores, SEO recommendations, and actionable tips to improve both readability and search performance.
A readability score measures how easy your content is to read and understand. These scores are calculated using mathematical formulas that consider sentence length, word length, and syllable count. Different formulas weight these factors differently, giving you a multi-dimensional view of your content's accessibility.
For SEO, readability matters because Google's algorithms increasingly reward content that satisfies user intent clearly and efficiently. High bounce rates caused by difficult-to-read content send negative engagement signals. Studies show that content written at an 8th–9th grade level consistently outperforms academic-level writing in organic search.
The most widely used readability formula. Higher scores mean easier reading. Developed by Rudolf Flesch in 1948 and still the industry standard.
Formula: 206.835 − (1.015 × avg words per sentence) − (84.6 × avg syllables per word)
Converts the Flesch formula into a US school grade level. A score of 8 means the content is appropriate for an 8th grader. Most web content targets grade 6–9. Aim for under 10 for general audiences.
Formula: (0.39 × avg words per sentence) + (11.8 × avg syllables per word) − 15.59
Measures complexity based on sentence length and percentage of "complex words" (3+ syllables). A score of 12 = US high school senior. Most major newspapers target a Fog score of 10–12. Aim for under 12 for online content.
Formula: 0.4 × (avg words per sentence + % of complex words)
Simple Measure of Gobbledygook. Highly accurate for texts over 30 sentences. Predicts the years of education needed to understand the text. Used extensively in healthcare and government communications. Aim for 10 or below for general audiences.
Uses character count rather than syllable counting, making it more reliable for automated tools. Correlates closely with Flesch-Kincaid Grade Level.
Keyword density is the percentage of times a keyword appears relative to the total word count. While Google doesn't confirm a specific target, SEO research consistently points to 1–2% as the sweet spot:
Keyword Density Checker — Detailed keyword frequency | Word Counter — Word and character counts | SERP Preview — Google result preview | Meta Tag Generator — HTML meta tags
For most blog content, aim for a Flesch Reading Ease of 60–70 (8th–9th grade level). This is "standard" difficulty — clear and accessible to the majority of adult readers without being overly simplified. Technical or B2B content may be lower (50–60). Content for beginners should aim for 70+.
Google has not confirmed readability as a direct ranking factor, but readability strongly influences user engagement metrics that Google does measure — dwell time, bounce rate, and pages per session. Content that is easy to read keeps visitors on your page longer, which signals quality. Additionally, readable content earns more backlinks and social shares.
The ideal keyword density is 1–2% for your primary keyword. Modern SEO prioritises semantic relevance over exact density percentages, so using related terms, synonyms, and contextually relevant phrases is more important than hitting an exact percentage. Focus on natural, helpful writing — not keyword engineering.
Each formula weights different factors. Flesch focuses on sentence length and syllables. Gunning Fog specifically targets polysyllabic (complex) words. SMOG is calibrated for longer texts. ARI uses character counts. A complete picture uses multiple scores together, which is why this tool shows all of them — look for the overall trend rather than any single number.
Research consistently shows that 1,500–2,500 words performs best for most informational topics. Posts over 2,000 words earn significantly more backlinks and rank for more long-tail keyword variations. However, word count should match user intent — a "how to tie a knot" post doesn't need 2,000 words, but a "complete guide to SEO" does.
The Gunning Fog Index estimates the years of formal education needed to understand a text. A score of 8 is accessible to most adults; 12 is the level of a US high school senior; 17+ indicates academic-level writing. For blog content, aim for under 12. Major newspapers average around 10–12.