Readability scores quantify how easily a human reader can understand written content. Search engines reward clear, accessible writing with higher engagement metrics, lower bounce rates, and improved voice search visibility.
Popular Readability Formulas Breakdown
1. Flesch Reading Ease
Scores range from 0 to 100, where higher scores indicate easier readability:
- 90–100: Very Easy (5th-grade reading level)
- 60–70: Standard Plain English (8th to 9th grade) — Recommended for most websites
- 0–30: Very Difficult (Academic / Legal journal)
2. Flesch-Kincaid Grade Level
Translates reading difficulty directly into US school grade levels. A score of 8.0 means an eighth-grader can comprehend the text.
3. Gunning Fog Index
Calculates the proportion of complex words (words containing 3 or more syllables) relative to sentence length. Target a score between 8 and 12 for digital business writing.
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