The Flesch Reading Ease score, developed by Rudolf Flesch in 1948, rates text on a 0–100 scale where higher is easier. The formula is:
206.835 − 1.015 × (total words / total sentences) − 84.6 × (total syllables / total words)
The two ratios are the average sentence length and the average number of syllables per word. Longer sentences and wordier vocabulary both push the score down. As a worked example, take a passage of 100 words in 5 sentences with 150 syllables: average sentence length is 20, and syllables per word is 1.5. The score is 206.835 − 1.015 × 20 − 84.6 × 1.5 = 206.835 − 20.3 − 126.9 ≈ 59.6 — right at the edge of "plain English".
Interpretation bands are roughly: 90–100 very easy (grade 5), 60–70 plain English (grade 8–9), 30–50 difficult (college), and 0–30 very difficult (graduate/academic). For most online writing, target 60–70; marketing copy often aims higher, technical documentation lower. A key nuance: because syllables per word is heavily weighted, a single very long word can dent the score, and the formula rewards short sentences even when they are choppy. It also gives no credit for clear structure or familiar jargon. Flesch Reading Ease and Flesch–Kincaid Grade Level are built from the same inputs but expressed on opposite scales — one as a 0–100 ease score, the other as a school grade. See Flesch Reading Ease explained for a deeper walkthrough, or measure a draft's length statistics with our Word Counter.