Flesch Reading Ease Score
The Flesch Reading Ease score is a readability formula that measures how easy a piece of text is to read, based on average sentence length and average number of syllables per word.
Definition¶
The Flesch Reading Ease score is a numerical measure of how easy a text is to read, calculated from two inputs: average sentence length (in words) and average syllable count per word. Scores range from 0 to 100 — higher scores indicate easier reading.
Formula¶
Flesch Reading Ease = 206.835 − (1.015 × average sentence length) − (84.6 × average syllables per word)
Both factors penalize the score: longer sentences and longer words reduce the score. Shorter sentences and simpler vocabulary increase it.
Score Interpretation¶
| Score | Difficulty | Typical Reader |
|---|---|---|
| 90–100 | Very easy | 5th grade |
| 70–90 | Easy | 6th grade |
| 60–70 | Standard | 7th–8th grade |
| 50–60 | Fairly difficult | High school student |
| 30–50 | Difficult | College student |
| 0–30 | Very difficult | College graduate / professional |
Recommended Targets¶
- General web content: 60–70
- Business writing: 50–65
- Academic journals: 30–50
- Medical patient education: 65+
Limitations¶
The Flesch formula measures sentence and word length, not comprehension difficulty directly. A text composed entirely of short sentences with short words will score 100 regardless of whether the ideas are simple. Technical vocabulary scores poorly even when unavoidable. The score is a useful proxy — not a complete measure of quality.
Flesch-Kincaid Grade Level¶
A closely related formula, Flesch-Kincaid Grade Level, uses the same inputs to produce a US school grade level rather than a 0–100 score. A grade level of 9 corresponds roughly to a Flesch score of 60.