What readability formulas are used?

The tool calculates Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog Index, and SMOG Index, the four most widely used readability metrics.

What score should I aim for?

For general web content, a Flesch Reading Ease score of 60 to 70 is ideal. Academic writing typically scores lower, while children's content scores higher.

Is my text sent to a server?

No. All calculations run entirely in your browser.

How much text do I need for an accurate score?

Readability formulas work best with at least 100 words. Very short texts can produce unreliable scores.

Readability checker

Readability checker is a text tool that scores prose against established readability metrics. It computes Flesch Reading Ease, Flesch-Kincaid grade level, Gunning Fog, and SMOG indexes, updates as you type, and includes estimated reading time. The tool runs in your browser.

Paste some text above to see readability stats.

Analysis modes

Direct links for each readability metric.

Flesch-Kincaid readability test

Check your text's Flesch Reading Ease and Flesch-Kincaid Grade Level. Instant readability score, entirely in your browser.

Reading time estimator

Estimate how long it takes to read your text at different reading speeds. Instant, in your browser.

Grade level checker

Check what grade level your writing targets using the Flesch-Kincaid formula. Paste any text for an instant score.

How to check text readability

Paste your article, document, or copy into the input area.
The tool calculates readability scores instantly, including Flesch Reading Ease and Grade Level.
Review the metrics to understand how easy or difficult your text is to read.
Edit your text and watch the scores update in real time.

Common uses

Checking that web content is accessible to a general audience before publishing, use word counter to check length at the same time
Simplifying technical documentation to make it readable for non-expert users
Meeting readability standards for legal, medical, or government documents. The text diff helps compare the original and simplified versions side by side

Technical specification

Algorithm or formula: Flesch Reading Ease 206.835 - 1.015(words/sentences) - 84.6(syllables/words) (Flesch, 1948); Flesch-Kincaid Grade Level 0.39(words/sentences) + 11.8(syllables/words) - 15.59 (Kincaid et al., 1975); Gunning Fog Index (Gunning, 1952); SMOG Index (McLaughlin, 1969).
Browser API or library: Pure JavaScript; custom syllable counter using vowel-cluster heuristics with adjustments for silent E and consonant suffixes.
Input limits: No hard cap; metrics work best at 100+ words. Below ~30 words, scores become statistically unreliable.
Output: Numeric scores for each metric, a US grade-level label, estimated reading time at 200-250 wpm, plus word, sentence, and syllable counts.
Known limitations: Syllable counting is heuristic and approximate; uncommon words can be misjudged. Scores are calibrated for English text.

Frequently asked questions

What readability formulas are used?: The tool calculates Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog Index, and SMOG Index, the four most widely used readability metrics.
What score should I aim for?: For general web content, a Flesch Reading Ease score of 60 to 70 is ideal. Academic writing typically scores lower, while children's content scores higher.
Is my text sent to a server?: No. All calculations run entirely in your browser.
How much text do I need for an accurate score?: Readability formulas work best with at least 100 words. Very short texts can produce unreliable scores.

Reviewed and tested May 26, 2026.