Readability Checker: Flesch-Kincaid Score & How to Write Clearly
Quick Answer
- *Readability measures how easy text is to understand, scored on formulas like Flesch-Kincaid that weigh sentence length and syllable count.
- *Most web content should score 60–70 on the Flesch Reading Ease scale (roughly grade 7–8).
- *The fastest fixes: shorter sentences, simpler words, active voice, subheadings, and bullet points.
- *According to Nielsen Norman Group, users read only 20–28% of words on a web page — clarity is not optional.
What Is Readability and Why Does It Matter?
Readability is how easily a reader can understand written text. It depends on word choice, sentence length, structure, and the match between your vocabulary and your audience's background knowledge. A document is readable not just when it's grammatically correct, but when the intended reader can process it quickly and accurately.
The numbers are stark. According to the U.S. Department of Education's 2019 National Assessment of Adult Literacy, roughly 54% of American adults read below a 6th-grade level. A separate analysis by the National Center for Education Statistics found the average U.S. adult reads at approximately an 8th-grade level. Write above that, and you lose more than half your audience — not because they're unintelligent, but because cognitive load limits how much effort people will invest in deciphering prose.
Nielsen Norman Group's eye-tracking research found that users read only 20–28% of wordson a given web page. People scan. They pick up headers, bolded phrases, and short sentences. Long, dense paragraphs get skipped. That's not a content marketing opinion — it's documented behavior across thousands of usability studies.
Plain language research reinforces this. The U.S. Plain Writing Act (2010) requires federal agencies to use clear, concise language precisely because dense government writing costs real money: misunderstood tax forms, unfollowed medical instructions, missed deadlines. A 2012 study published in Applied Ergonomics found that rewriting technical documents at a lower reading level reduced error rates by up to 36%.
The Flesch-Kincaid Reading Ease Score
Rudolf Flesch developed his Reading Ease formula in 1948 while working for the Associated Press. It was refined with J. Peter Kincaid in 1975 for the U.S. Navy to evaluate training manuals. Today it remains the most widely used readability formula in the world.
The formula:
Reading Ease = 206.835 − 1.015 × (words / sentences) − 84.6 × (syllables / words)
Two things drive the score: average sentence length (words per sentence) and average word length (syllables per word). Both pulling in the wrong direction — long sentences with polysyllabic vocabulary — tanks your score fast.
| Score | Difficulty | Typical Audience |
|---|---|---|
| 90–100 | Very Easy | 5th grade, children's books |
| 70–90 | Easy | 6th grade, conversational English |
| 60–70 | Standard | 7th–8th grade, most web content |
| 50–60 | Fairly Difficult | High school, professional blogs |
| 30–50 | Difficult | College level, technical writing |
| 0–30 | Very Difficult | Academic journals, legal documents |
Our Readability Checkercalculates this score instantly. Paste your text, and you'll see where you land.
The Flesch-Kincaid Grade Level
The Grade Level formula uses the same two variables (sentence length and syllables per word) but maps the output to a U.S. school grade rather than a 0–100 scale:
Grade Level = 0.39 × (words / sentences) + 11.8 × (syllables / words) − 15.59
A grade level of 8 means an 8th grader can understand the text. The U.S. federal government's plain language guidelines recommend grade 8 or below for all public-facing documents. The Wall Street Journal targets grade 11. Popular fiction like The Hunger Gamessits around grade 5–6. Most successful blogs and marketing copy cluster between grade 6 and grade 8.
Grade level is useful for compliance and accessibility. If you're writing healthcare content, the American Medical Association recommends materials at a 6th-grade reading level. Legal disclosures, ironically, often read at grade 16–18 — which is part of why most people don't read them.
Other Readability Formulas
Flesch-Kincaid isn't the only game in town. A few others worth knowing:
| Formula | What It Measures | Best For |
|---|---|---|
| Flesch Reading Ease | 0–100 ease score; higher = easier | General web content, marketing |
| Flesch-Kincaid Grade Level | US school grade equivalent | Compliance, healthcare, government |
| Gunning Fog Index | Years of education needed; penalizes complex words (3+ syllables) | Business writing, journalism |
| SMOG Index | Years of education; counts polysyllabic words in 30-sentence sample | Health literacy, patient materials |
| Coleman-Liau Index | Uses characters per word instead of syllables; more algorithmic | Automated analysis, digital tools |
The Gunning Fog Index, developed by Robert Gunning in 1952, calculates (average sentence length + percentage of complex words) × 0.4. A score of 12 equals a high school senior. Most business writing should target below 12; consumer-facing content below 8. Fog penalizes jargon hard — useful if you're editing technical content for a general audience.
The SMOG Index (Simple Measure of Gobbledygook) was designed specifically for health literacy assessment. It counts polysyllabic words across a 30-sentence sample and maps to grade levels. The CDC uses SMOG to evaluate patient education materials.
Readability Scores by Document Type
Different content types have different appropriate target scores. There's no universal “good” reading level — the right target depends on your audience and purpose.
| Document Type | Typical FK Grade Level | Flesch Reading Ease |
|---|---|---|
| Legal contracts | 18+ | 0–20 |
| Academic journals | 12–16 | 10–30 |
| Business reports | 10–12 | 30–50 |
| Newspaper articles | 7–8 | 55–65 |
| Web / blog content | 6–8 | 60–70 |
| Email marketing | 6–7 | 65–75 |
| Popular fiction | 5–7 | 70–80 |
| Children's content | 2–5 | 80–100 |
Notice the gap between legal writing (grade 18+) and popular fiction (grade 5–7). Legal language isn't difficult by accident — it's built for precision over accessibility. But most writing doesn't need that trade-off.
5 Ways to Improve Your Readability Score
1. Shorten Your Sentences
This is the single highest-leverage fix. Average sentence length has an outsized effect on every readability formula because it's a direct proxy for cognitive load. Aim for an average of 15–20 words per sentence. Mix short punchy sentences with longer ones for rhythm. When a sentence runs past 30 words, split it.
2. Choose Simpler Words
Replace multisyllabic words with shorter equivalents wherever meaning allows. “Use” beats “utilize.” “Show” beats “demonstrate.” “End” beats “terminate.” This isn't about dumbing down — it's about respecting your reader's attention. A 2022 Stanford study found that experts who simplified their vocabulary were perceived as more credible, not less. Complexity signals effort; clarity signals confidence.
3. Write in Active Voice
Passive constructions add words and distance the actor from the action. “The report was reviewed by the team” takes 8 words and 12 syllables. “The team reviewed the report” takes 6 words and 9 syllables — and it's cleaner. Active voice reduces word count, tightens sentences, and almost always produces a shorter average syllable count. Check your text for “was,” “were,” “been,” and “by” constructions as passive voice signals.
4. Add Subheadings
Subheadings don't directly change readability scores, but they break your content into scannable chunks that lower perceived reading effort. Nielsen Norman Group's research found that headings are among the most-read elements on any page— people use them to decide whether to read the body text at all. Use an H2 or H3 every 200–300 words. Keep heading text short (under 8 words if possible) and descriptive.
5. Use Bullet Points and Lists
Long lists embedded in prose force readers to parse sentence structure to extract items. Pull them out into bullets. Lists reduce visual density, signal parallel structure, and speed up scanning. Content marketing data from HubSpot shows that articles with three or more lists generate up to 70% more backlinksthan prose-only articles — likely because they're easier to reference and share.
You can track your word count as you edit with our Word Counter, or analyze your most-used vocabulary with the Word Frequency Counter to spot over-reliance on complex terms. Once your text is clean, the Whitespace Remover can strip extra spacing before you publish.
Check your text's readability score now
Try our free Readability Checker →Frequently Asked Questions
What is a good Flesch-Kincaid Reading Ease score?
A score of 60–70 is considered standard and appropriate for most web content. Scores above 70 are easy to read (popular fiction, consumer websites). Scores below 30 are very difficult (academic journals, legal contracts). Most digital content should target 60–70 for broad audience comprehension.
What does the Flesch-Kincaid Grade Level score mean?
The Flesch-Kincaid Grade Level maps your text to a US school grade. A score of 8 means an 8th grader can understand it. Most newspapers and popular websites target grade 6–8. Government plain language guidelines recommend grade 8 or below for public-facing documents.
How is the Flesch Reading Ease score calculated?
The formula is: 206.835 minus 1.015 times (total words divided by total sentences) minus 84.6 times (total syllables divided by total words). Longer sentences and more syllables per word lower your score. Shorter sentences and simpler words raise it toward the 100 maximum.
What readability score should a blog post have?
Blog posts aimed at a general audience should target a Flesch Reading Ease score of 60–70 (grade 7–8). Research from Nielsen Norman Group shows users scan web content rather than read it deeply, so plain, direct language improves both comprehension and time-on-page metrics.
Does readability affect SEO?
Google does not directly use readability scores as a ranking signal. But readability indirectly affects SEO through engagement metrics: clearer content reduces bounce rate, increases dwell time, and earns more backlinks. Plain language also improves featured snippet eligibility because it directly answers questions.
What is the Gunning Fog Index?
The Gunning Fog Index estimates the years of formal education needed to understand a text on first reading. It penalizes complex words (three or more syllables). A score of 12 equals a high school senior. Most business writing should target a Fog Index below 12; below 8 is ideal for consumer content.