What Is Flesch Reading Ease? (Readability Scores Explained)

Readability scores are numerical measures of how easy a piece of text is to read. The three most widely used formulas are Flesch Reading Ease, Flesch-Kincaid Grade Level, and the Gunning Fog Index.

Flesch Reading Ease

Developed by Rudolf Flesch in 1948, this score ranges from 0 to 100 — higher means easier.

Flesch RE = 206.835 − 1.015 × (words / sentences) − 84.6 × (syllables / words)

Score	Description	Typical audience
90 – 100	Very Easy	5th grade
80 – 90	Easy	6th grade
70 – 80	Fairly Easy	7th grade
60 – 70	Standard	8th–9th grade
50 – 60	Fairly Difficult	10th–12th grade
30 – 50	Difficult	College level
0 – 30	Very Difficult	Graduate / professional

Target for most web content: 60–70 (Standard). Blog posts, landing pages, and product descriptions aimed at a general adult audience should sit in this range.

Flesch-Kincaid Grade Level

The FK Grade Level translates the same underlying math into a US school grade — the grade level needed to understand the text with ease.

FK Grade = 0.39 × (words / sentences) + 11.8 × (syllables / words) − 15.59

A result of 8 means an 8th-grader could understand it. Marketing and consumer-facing content typically targets Grade 6–9. Legal and academic writing commonly reaches Grade 12–16.

Note: Flesch RE and FK Grade Level are inversely correlated — a high RE score corresponds to a low FK grade.

Gunning Fog Index

Developed by Robert Gunning in 1952, the Fog Index focuses on sentence length and complex words (words with 3+ syllables):

Fog = 0.4 × (words/sentences + 100 × complex_words/words)

Fog Index	Audience
≤ 8	Elementary / middle school
9 – 12	High school
13 – 16	College
17+	Graduate / academic

A score under 12 is generally considered accessible for a broad audience. Scores of 17 or above indicate highly specialised or academic prose.

Why readability matters for SEO

Google does not use readability scores as a direct ranking factor. However, readable content:

• Reduces bounce rate — readers who understand your content stay longer
• Increases social sharing — clear, accessible writing gets shared more
• Earns more backlinks — explainer content in plain language tends to attract citations
• Improves EEAT signals — authoritative content that communicates clearly builds trust

For content targeting a broad audience, a Flesch RE of ≥ 60 is a useful benchmark. Technical or professional audiences can tolerate lower scores.

Limitations

All three formulas use syllable counting — and syllable heuristics are imperfect. Different tools (including this one) use slightly different counting algorithms, so expect minor score differences between tools. Treat the scores as directional guides, not precise measurements.

Use the Readability Score Checker to calculate all three scores instantly from pasted text.