The Flesch Reading Ease formula
206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)
Rudolf Flesch published the formula in 1948. Higher scores mean easier text. Scores usually fall between 0 and 100, though very simple or very dense text can go beyond either end.
Score table
| Score | Difficulty | Typical reader |
|---|---|---|
| 90–100 | Very easy | Age 11 (US grade 5) |
| 80–89 | Easy | Grade 6 |
| 70–79 | Fairly easy | Grade 7 |
| 60–69 | Plain English | Grades 8–9 (age 13–15) |
| 50–59 | Fairly difficult | Grades 10–12 |
| 30–49 | Difficult | College |
| 10–29 | Very difficult | College graduate |
| 0–9 | Extremely difficult | Professional |
The Flesch–Kincaid grade level formula
0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59
J. Peter Kincaid and colleagues recalibrated Flesch’s inputs for the US Navy in 1975 to output a US school grade. A score of 8.0 means an average 8th grader (about 13–14 years old) should understand the text. It became a US military standard and is built into Microsoft Word.
How to raise your Flesch score
- Swap long words for short ones: use → utilise, help → assistance, start → commence.
- Split sentences over 25 words.
- Cut filler (very, really, basically) and wordy phrases (in order to → to).
- Prefer active voice, which is usually shorter.