Statistical
Flesch Reading Ease & Flesch-Kincaid Grade Level Readability Formulas
Calculate Flesch Reading Ease 206.835 - 1.015*(Words/Sentences) - 84.6*(Syllables/Words) and US school Flesch-Kincaid Grade Level 0.39*(Words/Sentences) + 11.8*(Syllables/Words) - 15.59 for editorial and compliance auditing.
Audit plain-language insurance, patient-consent, and SEO copy quantitatively!
US state insurance regulators, hospital IRB patient-consent boards (requiring <= 8th-grade reading level), and editorial teams rely on two complementary Rudolph Flesch / J. Peter Kincaid formulas driven by Average Sentence Length ASL = Words / Sentences and Average Syllables per Word ASW = Syllables / Words!
Flesch Reading Ease (FRE) scores copy on an inverse ~0–100+ ease scale (higher = easier to read, 60–70 = standard plain English): FRE = 206.835 - (1.015 * (Words / Sentences)) - (84.6 * (Syllables / Words))! Flesch-Kincaid Grade Level (FKGL) translates the same two ratios into equivalent US school grade years: FKGL = (0.39 * (Words / Sentences)) + (11.8 * (Syllables / Words)) - 15.59! Notice thatSyllables >= Words is a physical linguistic invariant (every word has at least 1 syllable!): for 180 words across 10 sentences (ASL = 18) with 270 syllables (ASW = 1.50), FRE = 61.67 and FKGL = Grade 9.13—and splitting sentences to 15 sentences with 234 syllables (ASW = 1.30) boosts FRE to 84.68!
| Document Sample (180 Words) | ASL (W/S) & ASW (Syl/W) | Flesch Reading Ease (FRE) | Flesch-Kincaid Grade (FKGL) |
|---|---|---|---|
| Standard Business Article | 10 sent (ASL=18), 270 syl (ASW=1.50) | 61.67 (Standard Plain English) | Grade 9.13 (~9th Grade) |
| Patient Consent Handout | 15 sent (ASL=12), 234 syl (ASW=1.30) | 84.68 (Easy Conversational) | Grade 4.43 (~4th-5th Grade) |
| Invalid Syllables < Words | Syllables < Words Check | Guarded Linguistic Error | "Invalid Counts (Syl >= Words > 0)" |
Flesch Reading Ease Score (0–100+ Plain-Language Scale)
Validates Words >= Sentences >= 1 and Syllables >= Words before computing 206.835 - 1.015*(W/S) - 84.6*(Syl/W).
=IF(OR(B2 <= 0, B3 <= 0, B2 < B3, B4 < B2), "Invalid Counts (Syl >= Words > 0)", ROUND(206.835 - (1.015 * (B2 / B3)) - (84.6 * (B4 / B2)), 2))Flesch-Kincaid US Grade Level (FKGL)
Computes 0.39*(Words/Sentences) + 11.8*(Syllables/Words) - 15.59.
=IF(OR(B2 <= 0, B3 <= 0, B2 < B3, B4 < B2), "Invalid Counts (Syl >= Words > 0)", ROUND((0.39 * (B2 / B3)) + (11.8 * (B4 / B2)) - 15.59, 2))Try the example
Use the original values or change them to test your understanding.