Free Readability Checker

A readability checker measures how hard your writing is to read. Paste your text and this tool returns a Flesch Reading Ease score from 0 to 100, a Flesch-Kincaid grade level, a Gunning Fog index and your reading time, then lists the long and passive sentences worth fixing first. It’s free, your text stays in your browser, and it asks for your email once to show results.

It’s built for founders, marketers and writers editing web pages, emails and guides for readers who skim.

Key takeaways

• Flesch Reading Ease runs from 0 to 100. Higher means easier. Aim for 60 or above on most web pages and emails.
• Two things drive every score: how long your sentences are and how long your words are.
• Fix the longest sentences first. The tool lists them for you, longest first.
• Formulas count; they don't understand. Use the score to find problems, then judge the fix yourself.

What this readability checker measures

The tool calculates three classic formulas plus some plain counts. All three formulas use sentence length; they differ in how they treat long words.

Score	Formula used in this tool	What it tells you
Flesch Reading Ease	206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words), kept between 0 and 100	Overall ease. Higher is easier
Flesch-Kincaid grade	0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59	The US school grade that matches the text
Gunning Fog index	0.4 × (words ÷ sentences + 100 × words of 3+ syllables ÷ words)	Years of schooling needed on a first read

Rudolf Flesch published Reading Ease in “A new readability yardstick” in the Journal of Applied Psychology in 1948. The grade-level version comes from a 1975 US Navy report by Kincaid, Fishburne, Rogers and Chissom, which recalculated three formulas for Navy training manuals. The Fog index comes from Robert Gunning’s 1952 book The Technique of Clear Writing.

• 531 Navy enlisted personnel tested to derive the Flesch-Kincaid grade formula, using 18 passages from training manuals Kincaid et al., US Navy, 1975
• 238 words per minute: average silent reading rate for English non-fiction, across 190 studies Brysbaert, Journal of Memory and Language, 2019

How it works

When you press Check readability, the tool does the following, all in your browser:

1. Counts words. A word is any run of letters or numbers, including apostrophes and hyphens inside it. So end-to-end counts as one word.
2. Splits sentences. It ends a sentence at ., ! or ? followed by a space, at a blank line, and at a line break before a bullet (-, * or •). It first removes the dots from common abbreviations (e.g., i.e., etc., vs., Mr., Mrs., Ms., Dr., Inc., Ltd.) so they don’t end a sentence early.
3. Counts syllables. It uses a common rule of thumb: words of three letters or fewer count as one syllable; otherwise it strips silent endings like -es, -ed and a final -e, then counts groups of vowels. It’s fast and close, but not a dictionary, so a word can be off by one.
4. Calculates the three scores with the formulas above.
5. Runs three checks. Average sentence length (20 words or fewer passes), sentences over 25 words (none passes), and possible passive sentences. A sentence is flagged as possibly passive when a form of “to be” (is, are, was, were, be, been, being, am) is followed by a word ending in -ed or -en, with an optional -ly word between. The check warns when more than one sentence, and more than 10% of all sentences, are flagged.
6. Estimates reading time at 230 words per minute, rounded, with a one-minute minimum. That’s close to the 238 words per minute Brysbaert’s 2019 review found for non-fiction.

The tool needs at least 20 words, because scores on one or two sentences swing wildly.

How to read your results

The headline is Flesch Reading Ease. The tool gives each range a label and a line of advice:

Reading Ease	Label	What it means	What to do
80–100	Easy	Plain enough for almost anyone to read quickly	Keep it. Check it isn’t choppy
60–79	Plain English	Clear for most adult readers	A good target for web pages and email
50–59	Fairly difficult	Readable, but some effort	Shorten sentences, swap a few long words
30–49	Difficult	Hard work for many readers	Split long sentences, replace long words
0–29	Very difficult	Reads like an academic paper	Rewrite the longest sentences first

The What to fix checks are where the editing starts. “Improve” next to average sentence length means your sentences average more than 20 words. “Improve” next to long sentences means at least one runs past 25 words; the list below shows up to five, longest first. Passive flags are hints, not errors. “The report was approved by the board” is passive; “The board approved the report” is clearer. But a phrase like “is often written” can trip the check, so read each one.

A worked example

Here’s a 38-word paragraph in two sentences, the kind that ends up on a lot of service pages:

Our comprehensive, end-to-end solution enables organizations to optimize their marketing operations through the strategic utilization of automation technologies. Implementation is typically completed by our experienced team within a timeframe that is determined by the complexity of existing infrastructure.

The tool counts 38 words, 2 sentences and 92 syllables.

• Words per sentence: 38 ÷ 2 = 19
• Syllables per word: 92 ÷ 38 = 2.421
• Reading Ease: 206.835 − (1.015 × 19) − (84.6 × 2.421) = 206.835 − 19.29 − 204.82 = −17.3, shown as 0 because the tool keeps scores between 0 and 100
• Grade: (0.39 × 19) + (11.8 × 2.421) − 15.59 = 7.41 + 28.57 − 15.59 = 20.4
• Fog: 19 of the 38 words have three or more syllables, so 0.4 × (19 + 50) = 27.6

Notice what didn’t trigger. Neither sentence is over 25 words, and the average of 19 passes the length check. The problem is the words: “organizations”, “utilization” and “implementation” are five syllables each. The second sentence is also flagged as passive (“is typically completed”).

Now the rewrite, 32 words in four sentences:

We set up marketing automation for you. Your team spends less time on manual work. Most setups take a few weeks. How long yours takes depends on the tools you already use.

• Words per sentence: 32 ÷ 4 = 8
• Syllables per word: 42 ÷ 32 = 1.3125
• Reading Ease: 206.835 − (1.015 × 8) − (84.6 × 1.3125) = 206.835 − 8.12 − 111.04 = 87.7 (Easy)
• Grade: (0.39 × 8) + (11.8 × 1.3125) − 15.59 = 3.12 + 15.49 − 15.59 = 3.0
• Fog: 3 complex words out of 32, so 0.4 × (8 + 9.4) = 7.0

Same message, shorter words, active voice. The reader knows who does the work and how long it takes.

Most of the copy I'm asked to fix isn't wrong, it's tiring. Long words and passive sentences make the reader do the work, and on a phone they just leave. My test is simple: read it out loud. If you run out of breath or lose the subject halfway through, rewrite it. A readability score only confirms what your ear already told you.

Best practices for readable web copy

Edit in this order

• Fix every sentence over 25 words first. Split it at "and", "which" or "because".
• Keep the average sentence at 20 words or fewer. Mix short and medium sentences so it doesn't sound robotic.
• Swap long words for short ones: use for utilize, help for facilitate, start for commence, to for in order to.
• Put the actor first. "We fixed the bug", not "The bug was fixed".
• Answer the reader's question in the first two or three sentences.
• Use lists and tables for steps and comparisons instead of long paragraphs.
• Check again after editing. Your score should move up; if it doesn't, look at word length.

Readable copy also makes a page easier to quote. When a page answers a question in two clear sentences, it’s simpler for a search engine or AI assistant to pull that answer out. Our guide on how to get cited in AI search covers the rest of that work, and our glossary entry on answer engine optimization explains the term. Good copywriting does the same job for people.

Common readability mistakes

Myth vs fact

MythA higher readability score always means better writing.

FactThe formulas count sentence and word length, not meaning. A page of very short sentences can score high and still say nothing useful.

MythGoogle ranks pages by readability score.

FactGoogle doesn't document any readability formula as a ranking factor. Clear writing helps because people can understand and use the page, which is what its helpful content guidance asks for.

MythTechnical topics can't be written plainly.

FactThe terms may need to stay, but the sentences around them can be short. Define a term once, then use it consistently.

Other mistakes worth avoiding:

• Chasing the number. Cutting every sentence to five words makes copy choppy and hard to follow. Aim for the Plain English band, not 100.
• Scoring the whole page with the menu in it. Navigation and footer text add short fragments that inflate your score. Paste only the body copy.
• Comparing scores across tools. Each tool counts syllables and sentences slightly differently. Track one tool over time.

Where to go next

If you’re rewriting service pages, start with the ones that matter most for leads. Our SEO team rewrites pages so they answer the search clearly, and our AI search optimization work structures them so AI assistants can quote them. A growth audit will tell you which pages to fix first.