Readability Formulas
Flesch Reading Ease
Higher score = easier to read. Score 60โ70 is "standard" (8th grade). Target 70+ for general audiences.
Score = 206.835 โ 1.015ร(words/sentences) โ 84.6ร(syllables/words)
Flesch-Kincaid Grade Level
Returns approximate US school grade level required to understand the text. Target โค 8 for general web content.
Grade = 0.39ร(words/sentences) + 11.8ร(syllables/words) โ 15.59
Gunning Fog Index
Estimates years of formal education required. Score 12 = high school senior. Target โค 12 for most content.
Fog = 0.4 ร [(words/sentences) + 100ร(complex words/words)]
SMOG Grade
Counts polysyllabic words. More accurate than Flesch-Kincaid for health/medical content.
SMOG = 3 + โ(polysyllabic count ร 30/sentences)
| Flesch Score | Difficulty | Audience |
|---|---|---|
| 90โ100 | Very Easy | 5th grade |
| 70โ90 | Easy | 6th grade |
| 60โ70 | Standard | 7โ8th grade |
| 50โ60 | Fairly Difficult | High school |
| 30โ50 | Difficult | College |
| 0โ30 | Very Difficult | Professional |