The main formulas
| Formula | Inputs | Output |
|---|---|---|
| Flesch Reading Ease | Words per sentence, syllables per word | 0–100 (higher is easier) |
| Flesch–Kincaid Grade | Same | U.S. school grade |
| Gunning Fog | Words per sentence, share of 3+ syllable words | Years of education |
| Coleman–Liau | Letters per word, sentences per 100 words | U.S. grade |
Flesch Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). Our Readability Checker computes all four.
What the numbers mean
| Flesch score | Level | Example |
|---|---|---|
| 90–100 | Very easy | Children’s books |
| 70–80 | Fairly easy | Popular fiction |
| 60–70 | Plain English | Most web content |
| 30–50 | Difficult | Academic prose |
| 0–30 | Very difficult | Legal and scientific papers |
A score is a guide to writing, not to quality. Easy is not always better: legal accuracy and technical precision may need longer words.
Limits
Readability formulas ignore meaning, vocabulary familiarity, structure, formatting and the reader’s prior knowledge. They work on English prose of sufficient length and misjudge headings, lists, code and non-English text. They are poor at judging whether a sentence is clear, only whether it is short. Use them as a prompt to review, not a verdict.
How to improve readability
- Split sentences longer than 25 words; check with the Sentence Counter.
- Replace long words with common ones.
- Use active voice and concrete verbs.
- Add headings, bullets and short paragraphs.
- Define technical terms once.
The Syllable Counter shows how syllables per word drive scores. Google does not use readability scores as a ranking factor, but clear writing serves readers; see Does Word Count Affect SEO?.
Frequently asked questions
What is a good Flesch Reading Ease score?
60 to 70 for general audiences.
Do these scores work for Urdu?
No. They are calibrated for English.
What grade level should I write for?
Grades 7 to 9 suit most web readers.