Table 1.

Formulas of the readability grade level indices and Flesch Reading Ease score.

Index	Formula
Automated Readability Index	4.71 × (characters/word) + 0.5 × (words/sentence) – 21.43
Coleman-Liau Index	0.0588 × (characters/100 words) – 0.296 × (sentences/100 words) – 15.8
Flesch-Kincaid Grade Level	(0.39 × words/sentence) + (11.8 × syllables/word) – 15.59
Gunning Fog index	0.4 × (words/sentence + percentage of ≥ 3-syllable words)
Simple Measure of Gobbledygook index	3 + (square root of≥3-syllable words count/30 sentences)
Average reading grade level (AGL)	Mean value of the above five indices
Flesch Reading Ease (FRE) score	206.835 – (1.015 × words / sentence) – (84.6 × syllables/word)