Readability
Checker.

Reading level describes how complex a piece of text is to understand. It is measured in US school grade equivalents (Grade 8 means an average 8th-grader can read it comfortably) or as a 0-100 ease score where higher means simpler. Both are calculated from sentence length and word complexity.

For general content and SEO writing, start with Flesch-Kincaid Grade Level and Flesch Reading Ease. They are the most widely used and the ones SEO tools like Yoast report. The other four formulas give additional perspectives. If they mostly agree, the result is reliable. If they diverge, check for unusually long sentences or a high density of technical terms.

For general-audience content such as blog posts, product pages, and emails, Grade 7-9 is the standard target. Grade 6 or below suits broad consumer audiences. Grade 10 and above is appropriate for professional, academic, or technical content where the reader is expected to have domain knowledge.

Both use the same two inputs: average sentence length and average syllables per word. Reading Ease outputs a 0-100 score where higher means simpler. Grade Level converts that into a US school grade. They are inverses of each other: a Reading Ease of 65 corresponds roughly to Grade 8.

Each formula weights its inputs differently and was designed for a specific type of writing. Gunning Fog penalizes complex words more heavily. Coleman-Liau and ARI measure word length in characters, not syllables. SMOG is calibrated for technical content. Differences between formulas are normal. The average across all six gives the most stable estimate.

The formulas were developed for English and are most accurate with English text. Syllable counting heuristics used in Flesch, Gunning Fog, and SMOG are language-specific. Coleman-Liau and ARI count characters, which works for any Latin-script language but scores may not translate meaningfully to grade levels in non-English educational systems.

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