Readability score checker — Flesch, Flesch–Kincaid, Fog, SMOG and more

How to use the readability score checker

1. Paste your text into Your text. Use several full sentences; a single line gives unstable scores.
2. Read the summary: Flesch Reading Ease, the Reading level band and the Flesch–Kincaid grade.
3. Check the counts behind them: words, sentences, syllables and complex words (three or more syllables).
4. Look at the table for all six scores, what each means, the exact formula and its original source.

What it does and when to use it

Use it when the reader matters: a report for parents, instructions for younger students, a science explanation, or an essay you suspect has grown dense. If the grade scores are well above your audience, shorten long sentences and swap long words for shorter ones, then paste the text again.

The essay word counter shows average sentence length and word count. The paragraph splitter breaks a wall of text into shorter paragraphs, which helps readers even though it does not change these scores. For notes that need tidying first, try the note formatter.

How it works

The tool counts words, sentences (at least one), syllables per word, complex words, letters and characters, then applies each formula:

• 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)]
• SMOG = 1.0430 × √(complex words × 30 ÷ sentences) + 3.1291
• Coleman–Liau = 0.0588 × L − 0.296 × S − 15.8, where L is letters and S sentences per 100 words
• ARI = 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43

Grade scores are US school grades: grade 9 is roughly age 14–15, and 13 or more is college level. The label uses the rounded score, so 12.97 and 13.0 are both college (US grade 13). Everything runs in your browser.

Worked examples

Very simple. “The cat sat on the mat. The dog ran to the park.” has 12 one-syllable words in 2 sentences. Flesch Reading Ease is 116.15, labelled Very easy, and Flesch–Kincaid is −1.45, shown as below grade 1.

Dense science. Three sentences about photosynthesis have 20 words, 44 syllables and 8 complex words. Flesch Reading Ease drops to 13.9, Very difficult, and Gunning Fog reaches 18.67, graduate level. Words such as “photosynthesis” and “respiration” do most of the damage.

The sample essay. The built-in paragraph about school start times (104 words, 8 sentences) scores 54.54, Fairly difficult, with a Flesch–Kincaid grade of 8.88, shown as US grade 9.

Limits and tips

• SMOG was designed for samples of 30 sentences; on short texts treat it as rough.
• Lists, headings and code confuse sentence counting. Paste plain paragraphs.
• The formulas were built for English. Scores for other languages are not meaningful.