Why readability matters
Most people skim online. If your sentences are long and full of complicated words, readers give up, especially on phones. Readability formulas estimate how much education a reader needs to understand a text easily. They are used by teachers choosing books, governments writing public information, businesses writing instructions and bloggers improving their articles. Clear writing also tends to keep visitors on a page longer.
How to check your text
- Paste at least a paragraph of English text. Longer samples (100 words or more) give more reliable scores.
- Read the Flesch Reading Ease score and the grade-level scores.
- Look at the list of long sentences and split them into shorter ones, then check again.
The formulas
Flesch Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)
Flesch-Kincaid Grade = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59
Gunning Fog = 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]
"Complex words" have three or more syllables. SMOG also counts complex words, while Coleman-Liau and the Automated Readability Index (ARI) use letters per word instead of syllables. Grade scores correspond to US school grades: 8 means an average 13- to 14-year-old can follow it.
What score should you aim for?
| Flesch score | Difficulty | Good for |
|---|---|---|
| 70–100 | Easy | Websites, instructions, marketing, children |
| 60–70 | Plain English | Most blog posts, news, emails |
| 30–50 | Difficult | Academic and technical papers |
| 0–30 | Very difficult | Legal and scientific specialist texts |
Frequently asked questions
Does it work for Hindi or other languages?
No. These formulas and the syllable counter were designed for English. Scores for other languages are not meaningful.
Why might the syllable count be slightly off?
English spelling is irregular, so syllables are estimated with rules. Small errors balance out over longer texts.
Is a lower grade always better?
Not always. Aim for the level of your readers. Simple does not mean childish: it means clear.