Readability Score Calculator

The readability score calculator runs six standard readability formulas over one pasted text sample and reports them together, because no single formula is the authority. You paste the copy once and the panels return the scores, the counts they are built from and a plain-language band for the result.

What is Readability Score Calculator?

The readability score calculator takes a block of text and applies six published formulas to it, then shows the intermediate counts on the same screen so a score can be argued with rather than just accepted.

• Flesch Reading Ease returns a 0 to 100 ease score rather than a grade: 206.835 minus 1.015 times words per sentence minus 84.6 times syllables per word.
• Flesch-Kincaid Grade gives a US school grade from 0.39 times words per sentence plus 11.8 times syllables per word minus 15.59.
• The Gunning Fog index treats any word of three syllables or more as complex and applies 0.4 times the sum of words per sentence and 100 times the complex share.
• SMOG, designed for health and consumer writing, takes 1.043 times the square root of complex words times 30 divided by sentences, plus 3.1291.
• Automated Readability Index uses characters instead of syllables: 4.71 times letters per word plus 0.5 times words per sentence minus 21.43.
• Coleman-Liau works from letters per 100 words and sentences per 100 words, weighted 0.0588 and 0.296 respectively.

Syllables are approximated the way the formulas were designed to be fed. A word is split into vowel groups, one group is subtracted for a silent final e that is not a consonant plus le ending, a further group is removed for a non-syllabic es or ed ending unless the vowel pair already forms a syllable of its own, and no word is ever allowed to fall below one syllable. Words and sentences are counted from the sample as typed, complex words are those reaching three syllables, and reading time is the word count at 200 words per minute, rounded up with a floor of one minute. Sentences break on a period, exclamation mark or question mark followed by whitespace or the end of the text, so an abbreviation that ends in a period counts as a sentence boundary.

• The syllable figure is an approximation, so the scores land close to, not identical to, a hand count; proper nouns and loanwords are the usual source of drift.
• Every formula here is calibrated on English prose, so writing in another language produces a number that means nothing.
• Only letters and digits are counted as words, so a line of punctuation or a row of symbols is skipped rather than treated as an error.
• The formulas read surface features only. They say nothing about whether a sentence makes sense, and short sentences of hard vocabulary can still score well.
• Nothing is highlighted sentence by sentence, so tracking down the clause that raised the grade means editing the text and running it again.

Treat the reading grade level figures as a spread rather than a target: the tool averages Flesch-Kincaid, Gunning Fog, the ARI and Coleman-Liau, and that average is the number to quote when someone asks what reading level a page needs. For regulated copy, health, legal or government text, quote the weakest formula instead of the average, because the reader you are protecting sits at the bottom of the range. Readability is only one axis of legibility: a score in the plain-English band still reads badly if the measure is too wide or the leading too tight, which is where the line height optimizer and the paragraph width optimizer take over.

How to use Readability Score Calculator

1. Paste or type the copy into the sample field. The default sample is replaced as soon as you type, and every score recomputes on each keystroke.
2. Read the counts first — words, sentences, syllables, complex words, words per sentence, syllables per word and reading time at 200 words per minute — since these are what the formulas consume.
3. Compare the six formula results and the average of the four grade-level scores in the interpretation panel, which also names the Flesch band the sample falls into.
4. Edit the copy in place and watch the scores move. Rewriting one clause is usually enough to shift a grade level, so re-run rather than estimate.

When to use Readability Score Calculator vs related tools

Reach for it when copy has to hit a stated reading level — a patient information sheet, a policy summary, a school text — or when a page reads heavy and you want the reason in numbers rather than opinion. It pairs naturally with the line height optimizer because a plain-English grade still reads poorly at tight leading, and with the paragraph width optimizer when the measure rather than the prose is what is tiring the reader. Where the concern is the reader's access needs rather than the writing, the font accessibility evaluator covers the styling side of the same problem.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

Frequently asked questions about Readability Score Calculator