Readability Scores Explained: How to Write for Every Audience

Not all readers are the same. A legal brief, a children's book, and a technical manual should be written at very different reading levels. Readability scores give you an objective measure of how difficult your writing is — and guide you toward the right level.

Flesch Reading Ease Score

Developed by Rudolf Flesch in 1948. Scores from 0 (very difficult) to 100 (very easy). Formula: 206.835 − (1.015 × words per sentence) − (84.6 × syllables per word)

• 90–100: Very easy (5th grade level, conversational)
• 70–80: Easy (7th grade, popular fiction)
• 60–70: Standard (8th-9th grade, plain English)
• 50–60: Fairly difficult (10th-12th grade)
• 30–50: Difficult (college level)
• 0–30: Very difficult (academic/technical)

Flesch-Kincaid Grade Level

Similar formula but outputs a US school grade level. Grade 8 = readable by an 8th grader. A score of 12 is a high school senior. US government plain language guidelines recommend grade 8 for public-facing content.

Gunning Fog Index

Estimates years of formal education required to understand text on first reading. Formula: 0.4 × (words/sentences + 100 × complex words/words). "Complex words" = words with 3+ syllables. Target under 12 for most writing.

Practical Tips to Improve Readability

• Keep average sentence length under 20 words
• Prefer short words over long ones (use instead of utilise)
• Use active voice instead of passive
• Break up paragraphs — aim for 3–4 sentences max
• Use bullet points for lists instead of complex sentences

Analyse your writing readability with our Word Counter tool.