Free Readability Checker and Reading Level Calculator

A readability checker applies mathematical formulas to sentence length, word length, character count, and estimated syllables. This browser tool reports Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, Automated Readability Index, and Coleman-Liau estimates together.

Your pasted text is processed in your browser. It is not uploaded or saved, and no account is required.

To check readability, paste a representative English passage and compare the

six formula results rather than relying on one score. The checker explains the

underlying sentence, word, character, and syllable counts so you can decide

whether a revision improves clarity for the intended reader.

How to Check Readability

1. Paste a complete English passage.
2. Review the six formula results.
3. Check the underlying words, sentences, characters, syllables, and complex-word counts.
4. Compare formulas instead of treating one score as a verdict.
5. Read the passage yourself before changing required terminology.

Longer samples generally provide more stable averages than one or two sentences.

Flesch Reading Ease

Flesch Reading Ease uses words per sentence and syllables per word. Higher scores usually indicate easier English text; lower scores indicate more demanding text.

The formula is:

206.835 − 1.015 × words per sentence − 84.6 × syllables per word

The score can fall outside 0–100 for unusual samples. This tool displays the calculated value rather than silently forcing it into that range.

Flesch-Kincaid Grade

Flesch-Kincaid Grade uses the same inputs with different coefficients:

0.39 × words per sentence + 11.8 × syllables per word − 15.59

The result is commonly interpreted as an approximate US grade level. It is not an official placement or assessment.

Gunning Fog

Gunning Fog combines sentence length with the percentage of complex words:

0.4 × (words per sentence + percentage of complex words)

This implementation treats words with three or more estimated syllables as complex, while excluding some common suffix patterns. Proper names and specialist terms can still raise the result even when the intended audience understands them.

SMOG

SMOG estimates grade level from polysyllabic words and sentences:

1.043 × square root of (complex words × 30 ÷ sentences) + 3.1291

SMOG is often applied to longer samples. A short passage can produce an unstable estimate, so the result should be treated cautiously.

Automated Readability Index

The Automated Readability Index uses characters rather than syllables:

4.71 × characters per word + 0.5 × words per sentence − 21.43

Because it avoids syllable estimation, it provides a useful comparison with the pronunciation-based formulas.

Coleman-Liau Index

Coleman-Liau also uses letters and sentences:

0.0588 × letters per 100 words − 0.296 × sentences per 100 words − 15.8

It can differ from ARI because the coefficients and normalization are different.

Why the Scores Differ

Each formula models difficulty with a limited set of observable features. None directly measures:

• factual accuracy;
• logical structure;
• prior knowledge;
• visual layout;
• cultural context;
• whether a technical term is necessary;
• whether a reader can apply the information.

A passage can score as easy while being misleading, or score as difficult because it accurately uses specialist vocabulary.

English Syllable Estimates

The syllable-based formulas require pronunciation data. This browser tool uses an English spelling heuristic rather than a complete pronunciation dictionary. Silent letters, abbreviations, names, loanwords, and irregular words can be counted differently from spoken English.

That makes Flesch, Flesch-Kincaid, Gunning Fog, and SMOG estimates. ARI and Coleman-Liau use characters or letters and do not depend on the syllable heuristic.

How to Use Readability Results

Use scores to locate questions, not to automate every edit:

1. Are sentences carrying several unrelated ideas?
2. Can important information appear earlier?
3. Are unfamiliar terms defined on first use?
4. Are long words required for accuracy?
5. Do headings and lists expose the structure?
6. Would an example clarify an abstract statement?

Use the word counter for document totals, the sentence counter for sentence-length distribution, and the keyword density checker for repeated terms.

Use the passive voice checker to review likely be/get auxiliary plus past-participle patterns sentence by sentence.

What the Results Mean

Privacy and Limitations

The checker runs locally after the page loads and does not send pasted text to Humanizer PRO.

Limitations include:

• formulas are designed primarily for English;
• syllables are estimated without a full pronunciation dictionary;
• sentence segmentation can differ around abbreviations;
• headings, bullets, and fragments affect averages;
• short samples are volatile;
• grade outputs are estimates, not reader testing;
• scores do not measure truth, usefulness, or accessibility compliance;
• the tool does not inspect URLs or documents;
• it does not make search-ranking predictions.

Frequently Asked Questions

Is this readability checker free?

Yes. It is free, needs no account, and processes text in your browser.

Which formulas are included?

Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, Automated Readability Index, and Coleman-Liau.

Is a reading-level score exact?

No. It is a formula estimate based on surface features of the passage.

Why do the grade scores disagree?

They use different inputs and coefficients. Comparing several scores exposes that uncertainty.

Does this support languages other than English?

The interface accepts text, but the syllable heuristic and formula interpretations are designed for English. Results for another language should not be treated as valid.

Does it save my text?

No. The browser tool does not upload or save pasted text.

Can readability predict comprehension?

No. Only testing with the intended readers can evaluate comprehension directly.

Is readability a Google ranking factor?

This calculator does not make ranking claims. Write to answer the reader’s task accurately and clearly rather than chasing one formula score.

Use Formulas as Signals, Not Instructions

Compare the scores, inspect the underlying sentence and word patterns, and revise only where the change helps the intended reader without weakening accuracy.

Humanize up to 300 words and review the editable result →