Readability Test

When to use Readability Test

• Auditing landing page copy: Long sentences and multisyllabic words increase bounce rate on landing pages. Check readability before publishing and simplify anything scoring below 60 on the Flesch scale.
• Checking help documentation and error messages: Error messages and help text must be understood immediately under stress. Grade 6-7 is the appropriate target for UI copy and support content.
• SEO content optimisation: Google's quality guidelines do not specify a readability score, but content that is difficult to read has higher bounce rates - an indirect ranking signal. Match complexity to your audience's expected reading level.
• Legal and compliance document review: Many jurisdictions require consumer-facing terms, privacy policies, and financial disclosures to meet a minimum readability threshold. Use Flesch Reading Ease as a baseline check.

How readability scores are calculated and what they mean

The Readability Test calculates three standard readability scores: the Flesch Reading Ease score, the Flesch-Kincaid Grade Level, and the Gunning Fog Index. Each formula uses counts of words, sentences, and syllables derived from your text.

The Flesch Reading Ease score is calculated as: 206.835 - (1.015 × average words per sentence) - (84.6 × average syllables per word). Scores range from 0 to 100. A score of 60-70 is considered plain English, appropriate for general web content. A score below 30 indicates academic or legal complexity; above 80 is considered very easy to read (children's books, simple instructions). The US Department of Defense and many insurance regulators require consumer-facing documents to score above 60.

The Flesch-Kincaid Grade Level converts the same word and syllable data into a US school grade equivalent: (0.39 × average words per sentence) + (11.8 × average syllables per word) - 15.59. A score of 8 means the text is appropriate for an eighth-grade reader. Web content aimed at a general audience should target grade 6-8. The Gunning Fog Index uses a different approach, counting "complex words" (words with three or more syllables, excluding proper nouns and compound words) as a proxy for difficulty. Syllable counting is performed using a dictionary-based approach with a fallback vowel-cluster heuristic for words not found in the dictionary.