Readability Checker — Flesch-Kincaid & More

Analyze any text and get instant readability scores: Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, and detailed text statistics.

Flesch Reading Ease Score Reference

Score Difficulty Typical Audience
90–100Very Easy5th grade, conversational
70–90Easy6th–7th grade, consumer content
60–70Standard8th–9th grade, news articles
50–60Fairly Difficult10th–12th grade, professional
30–50DifficultCollege level
0–30Very DifficultAcademic / professional specialist

What Is the Flesch-Kincaid Readability Test?

The Flesch-Kincaid tests are a pair of readability formulas developed by Rudolph Flesch and J. Peter Kincaid in the 1970s for the U.S. Navy. They measure how easy or difficult a piece of English text is to read, based on average sentence length and average syllables per word.

Flesch Reading Ease produces a score from 0 to 100. Higher scores mean easier reading. A score of 60–70 corresponds to plain English suitable for most adults. A score below 30 indicates academic or highly technical text.

Flesch-Kincaid Grade Level maps the same calculation to a US school grade level. A score of 8.0 means the text is appropriate for an 8th grader (age 13–14). Most web content targets a grade level of 6–9.

What Is the Gunning Fog Index?

The Gunning Fog Index, developed by Robert Gunning in 1952, estimates the years of formal education needed to understand text on first reading. It places more weight on "complex words" — words with three or more syllables. A Fog score of 12 corresponds to a high school senior; scores above 17 are considered very difficult.

Ideal Readability for Different Content Types

  • Blog posts and web content: Flesch 60–70, Grade Level 7–9. Aim for clear, short sentences and common words.
  • News articles: Flesch 60–70. Most newspapers target 8th grade reading level.
  • Marketing copy and landing pages: Flesch 70–80. The clearer and simpler, the better conversion rates.
  • Academic papers: Flesch 20–40 is normal. The complexity is inherent to the subject matter.
  • Legal documents: Flesch 10–30. Notoriously complex — plain-language initiatives aim to improve this.

Using This Tool to Check AI-Generated Content

AI models often produce text that reads at a higher grade level than intended — they favor longer sentences and multi-syllable words. Use this readability checker to verify that AI-generated blog posts, emails, and landing pages are accessible to your target audience. If the grade level is above 10, simplify sentence structure and replace complex words with common alternatives.

Frequently Asked Questions

How many sentences do I need for an accurate score? +
At least 3–5 sentences for a meaningful result. Single sentences or very short text will produce unreliable scores because the formulas rely on averages across multiple sentences. For the most accurate analysis, test at least 200 words.
Does a lower grade level mean lower quality? +
No. Low grade level means accessible writing, not simplistic writing. Most professional writers aim for grade level 6–9 for general audiences. Clear, direct writing is a skill. Academic complexity is only appropriate when the audience and subject genuinely require it.
What is a good Flesch score for a blog post? +
Aim for a Flesch Reading Ease score of 60–70 for most blog content. This corresponds to a standard difficulty level appropriate for adults reading online. Scores of 70–80 are even better for broad audiences.
Why does this tool calculate syllables differently? +
Syllable counting in plain JavaScript uses a heuristic algorithm (counting vowel groups) rather than a full dictionary. The estimates are accurate for most English words but may be slightly off for unusual words, proper nouns, or technical terms. The overall readability scores remain reliable for typical content.