Readability Score Checker
A readability checker scoring Flesch Reading Ease, Flesch–Kincaid, Gunning Fog and Coleman–Liau, and listing the sentences that produced the score.
Analyzed in this tab — the text is never uploaded.
What Readability Score Checker Does
Readability formulas all work the same way: they count sentence length and word difficulty, and combine the two into a number. Flesch Reading Ease runs 0 to 100 with higher meaning easier; Flesch–Kincaid converts the same inputs into a US school grade; Gunning Fog estimates the years of education a reader needs; Coleman–Liau gives a grade level from letters per word instead of syllables. None of them read your text; they count it.
That is worth understanding because it tells you what moves a score. Both Flesch measures are driven by average sentence length and average syllables per word, and nothing else. Gunning Fog swaps syllable average for the proportion of words with three or more syllables. Sentence length is the term all three share, which is why splitting long sentences changes a score far more than swapping vocabulary.
So the useful output is not the number, it is which sentences produced it. This lists your longest ones, because a text scoring badly usually has a handful of sprawling sentences rather than uniformly hard prose, and fixing three of them can move every score at once.
One honest caveat about all of it: these formulas measure how demanding prose is to decode, not whether it is any good, accurate or worth reading. A text can score beautifully and say nothing at all.
How to Use Readability Score Checker
- Paste or type your text
- View readability scores in real-time
- Check the grade level and difficulty assessment
- Adjust your text for your target audience
Formula Used by Readability Score Checker
The four formulas
Ease = 206.835 − 1.015·ASL − 84.6·ASW Grade = 0.39·ASL + 11.8·ASW − 15.59 Fog = 0.4·(ASL + 100·(complex ÷ words)) CLI = 0.0588·L − 0.296·S − 15.8
- ASL
- average sentence length: words divided by sentences
- ASW
- average syllables per word
- complex
- words of three or more syllables, Gunning’s own definition, counted in syllables rather than letters
- L
- letters (and digits) per 100 words (Coleman–Liau)
- S
- sentences per 100 words (Coleman–Liau), the same sentence-length signal as ASL, inverted
Worked example
A 200-word passage in 10 sentences, 320 syllables, 24 words of three or more syllables.
- ASL = 200 ÷ 10 = 20; ASW = 320 ÷ 200 = 1.6
- Ease = 206.835 − 1.015×20 − 84.6×1.6 = 206.835 − 20.3 − 135.36
- Grade = 0.39×20 + 11.8×1.6 − 15.59 = 7.8 + 18.88 − 15.59
- Fog = 0.4 × (20 + 100 × 24÷200) = 0.4 × (20 + 12)
Result: Ease 51.2 (fairly difficult), grade 11.1, Fog 12.8: all three saying roughly "late secondary school".
Flesch Reading Ease, interpreted
| Score | Level | Typical of |
|---|---|---|
| 90–100 | Very easy | Writing for young children |
| 80–89 | Easy | Conversational English |
| 70–79 | Fairly easy | Popular fiction |
| 60–69 | Plain English | Where most general-audience writing aims |
| 50–59 | Fairly difficult | Quality journalism, trade press |
| 30–49 | Difficult | Academic and professional writing |
| Below 30 | Very difficult | Legal and technical documents |
What actually changes a score
All four formulas share sentence length, which is why it dominates.
| Change | Effect |
|---|---|
| Splitting a 40-word sentence into two | Large — it moves the term every formula shares |
| Cutting one long sentence entirely | Large |
| Replacing "utilize" with "use" | Small, unless done throughout |
| Removing a subordinate clause | Moderate — shortens the sentence and often drops long words |
| Adding headings and paragraph breaks | None to these scores, though it genuinely helps readers |
How to Read Your Result
Aim for a range, not a number
General audiences are usually well served somewhere in the 60s on Reading Ease, which is around a 9th-grade level. Technical documentation for specialists can sit lower without being a problem. Writing to hit an exact score produces stilted prose, which is the one thing that reliably makes text harder to read.
Short samples give unstable numbers
These are averages, so a handful of sentences can swing wildly; a single long one moves everything. Below about five sentences the figure is arithmetic rather than information, and the tool says so rather than presenting it as a finding.
Syllable counting is an estimate
Without a pronunciation dictionary, syllables are approximated by counting vowel groups with corrections for silent endings. It is what these formulas assume and it is not exact: "business" counts as three here and is two in speech. Small differences between readability tools almost always come from this.
Limitations & Accuracy Notes
- English only. The coefficients were derived for English and produce meaningless numbers for other languages.
- Syllables are estimated rather than looked up, so counts differ slightly between tools.
- The formulas measure decoding difficulty. They say nothing about clarity, accuracy, structure or value.
- They ignore everything that genuinely helps a reader: headings, lists, paragraph length, and whether the sentences are in a sensible order.
- Lists, code blocks and tables are treated as prose, which distorts the sentence average.
- Proper nouns and familiar jargon are counted as complex words, which Gunning’s original definition excludes; no automated tool can reliably tell which is which.
Frequently Asked Questions
What is a Flesch-Kincaid score?
The Flesch-Kincaid readability test estimates the U.S. school grade level needed to understand a text. A score of 8.0 means an 8th-grader can understand it. Lower scores = easier to read.
What readability score is ideal for web content?
For general web audiences, targeting a 7th to 8th grade reading level (Flesch-Kincaid score around 60–70) ensures maximum clarity and user engagement.
Does a low grade-level score mean the writing is worse?
No. A lower Flesch-Kincaid grade level means the text is easier to read, which is usually the goal for general web content, and it says nothing about the quality of the writing.
Does this analyze grammar or just readability?
Just readability: it measures sentence length and word complexity to estimate reading difficulty. It does not check grammar, spelling, or factual accuracy.
Which score should I pay attention to?
Flesch Reading Ease is the most widely recognized and the easiest to explain to someone else. Gunning Fog maps roughly onto years of education. They usually agree on direction, so the informative signal is whether an edit moved the score, not its absolute value.
What score should I aim for?
It depends entirely on the audience. General web writing often targets a reading ease around 60 to 70; technical documentation for specialists will score much lower and should. Writing toward a number rather than toward your reader produces worse text.
Why does my technical writing score badly?
Because these formulas count syllables and sentence length, and accurate technical vocabulary is polysyllabic. "Authentication" is four syllables whether or not it is the correct word. A low score on specialist writing often means it is precise, not that it is bad.
Can a readability score be gamed?
Trivially. Chopping every sentence in two and swapping long words for short ones improves the score without improving anything else. That is the clearest evidence these are surface measures, useful as a prompt to reread rather than as a target.
Do these formulas measure comprehension?
No. They measure two proxies for difficulty and are blind to organization, coherence, accuracy, and whether the argument makes sense. A passage of fluent nonsense in short sentences scores well.
Is my text sent anywhere?
No. All analysis runs in your browser.
References & Further Reading
- plainlanguage.gov — Federal Plain Language Guidelines — What actually makes government and professional writing readable, most of which no formula measures
- Readable — the Gunning Fog Index — States the formula and the three-or-more-syllables definition of a complex word
- Readable — the Coleman–Liau Index — Coleman and Liau (1975) built the index on letters rather than syllables, for machine scoring