Readability Formulas

Flesch Reading Ease

Higher score = easier to read. Score 60–70 is "standard" (8th grade). Target 70+ for general audiences.

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

Flesch-Kincaid Grade Level

Returns approximate US school grade level required to understand the text. Target ≤ 8 for general web content.

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

Gunning Fog Index

Estimates years of formal education required. Score 12 = high school senior. Target ≤ 12 for most content.

Fog = 0.4 × [(words/sentences) + 100×(complex words/words)]

SMOG Grade

Counts polysyllabic words. More accurate than Flesch-Kincaid for health/medical content.

SMOG = 3 + √(polysyllabic count × 30/sentences)
Flesch ScoreDifficultyAudience
90–100Very Easy5th grade
70–90Easy6th grade
60–70Standard7–8th grade
50–60Fairly DifficultHigh school
30–50DifficultCollege
0–30Very DifficultProfessional

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