How to Improve Text Readability: Scores, Formulas & Practical Tips
What Is Readability and How Is It Measured?
Readability is the ease with which a reader can understand written text. It depends on two main factors: the complexity of vocabulary (measured by syllable count or character count) and the complexity of syntax (measured by sentence length). Unlike legibility, which concerns typefaces and layout, readability is about the language itself.
Readability formulas were first developed in the 1940s and 1950s for the U.S. military. The goal was to ensure that training manuals could be understood by recruits with varying education levels. Today, these same formulas power readability checkers used by writers, editors, healthcare communicators, and UX professionals worldwide.
A readability score does not measure the quality of ideas, the accuracy of information, or the persuasiveness of an argument. It measures how easily your audience can process your words. The best ideas fail if the audience cannot parse the sentences that contain them.
Why Readability Matters: The Data
The stakes are higher than most writers realize. According to the National Center for Education Statistics, 43% of U.S. adults read at a basic or below-basic literacy level. That means nearly half your potential audience struggles with text written above an 8th-grade level.
The consequences of poor readability extend across every domain:
- Healthcare: Patients who cannot understand discharge instructions are 3 times more likely to be readmitted within 30 days. The American Medical Association recommends all patient materials be written at a 6th-grade level.
- Legal: Plain-language laws in over 30 countries now require government documents to be written clearly. The SEC found that simplified prospectuses increased investor comprehension by 40%.
- Web content: Nielsen Norman Group research shows users read only 20-28% of words on a typical web page. Simpler text increases the percentage read and the time spent on page.
- Business: A study by the Literacy Project found that companies lose an estimated $400 billion annually in the U.S. due to poor workplace communication, much of it caused by unnecessarily complex writing.
- SEO: Google's Helpful Content system favors content that is accessible to the intended audience. Pages with better readability tend to have lower bounce rates and higher dwell times, both positive engagement signals.
"Any fool can make something complicated. It takes a genius to make it simple." — Woody Guthrie
Readability Analyzer Tool
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Readability Scores
Text Analysis
Simplification Suggestions
6 Readability Formulas Explained
Each formula uses a slightly different approach to estimate reading difficulty. Understanding the math behind them helps you know which levers to pull when improving your text.
1. Flesch Reading Ease (FRE)
Scale: 0 to 100. Higher = easier. A score of 60-70 is considered plain English, readable by 13- to 15-year-olds. Scores above 90 indicate text understandable by a 5th grader. Scores below 30 are best understood by university graduates.
Invented: Rudolf Flesch, 1948. Originally designed to assess the readability of newspapers and adult reading materials.
Best for: General content, marketing copy, blog posts. The most widely recognized readability metric.
2. Flesch-Kincaid Grade Level (FKGL)
Scale: U.S. school grade level. A score of 8.0 means an 8th grader can understand the text. Uses the same inputs as Flesch Reading Ease but produces an inversely correlated grade-level output.
Invented: J. Peter Kincaid and team, 1975. Commissioned by the U.S. Navy to ensure technical manuals were accessible to enlisted personnel.
Best for: Setting grade-level targets for technical documentation, educational materials, and government communications.
3. Gunning Fog Index
Scale: Years of formal education needed. A Fog Index of 12 requires a high-school senior's reading level. "Complex words" are defined as words with 3 or more syllables, excluding proper nouns, familiar jargon, and compound words.
Invented: Robert Gunning, 1952. Developed for newspaper editors and business writers.
Best for: Business writing and journalism. Particularly sensitive to jargon-heavy prose.
4. Coleman-Liau Index (CLI)
Where: L = average number of letters per 100 words, S = average number of sentences per 100 words.
Scale: U.S. school grade level. Unlike Flesch-Kincaid and Gunning Fog, Coleman-Liau uses character counts instead of syllable counts, making it more reliable for automated scoring since syllable counting requires heuristics.
Invented: Meri Coleman and T.L. Liau, 1975.
Best for: Machine-processed text analysis. Eliminates syllable-counting ambiguity.
5. SMOG Index (Simple Measure of Gobbledygook)
Scale: Years of education needed. Counts polysyllabic words (3+ syllables) across a sample of 30 sentences. Considered more conservative than other formulas; it estimates the grade level needed for 100% comprehension rather than 50-75%.
Invented: G. Harry McLaughlin, 1969.
Best for: Health literacy materials. The gold standard for patient education documents, recommended by the U.S. Department of Health and Human Services.
6. Automated Readability Index (ARI)
Scale: U.S. school grade level. Like Coleman-Liau, ARI uses character counts rather than syllable counts. It was designed for real-time monitoring on electric typewriters, where counting characters is trivial.
Invented: Senter and Smith, 1967. Originally developed for the U.S. Air Force.
Best for: Automated, real-time readability scoring. Fast to compute since it avoids syllable estimation.
No single formula is definitive. Each one captures a slightly different aspect of text complexity. For the most accurate assessment, use multiple formulas and look at the consensus. If all six agree your text is at grade level 12, you can be confident it requires a college-level education to read comfortably.
Industry Readability Benchmarks
Different contexts demand different readability levels. Oversimplifying a legal contract is as problematic as writing a patient handout at a graduate level. Here are evidence-based targets by industry:
| Content Type | Target Grade | Flesch Ease | Rationale |
|---|---|---|---|
| Patient health information | Grade 5-6 | 70-80 | AMA & HHS recommendation; 36% of adults have limited health literacy |
| Consumer marketing | Grade 6-7 | 65-75 | Maximum audience reach; mirrors successful ad copy |
| Blog posts & web content | Grade 7-8 | 60-70 | Standard for plain English; balances depth with accessibility |
| Newspaper articles | Grade 8-9 | 55-65 | AP Stylebook standard; front-page NYT averages grade 9 |
| Technical documentation | Grade 8-10 | 45-60 | Audience has domain knowledge; clarity still essential |
| Business & financial reports | Grade 10-12 | 35-50 | Professional audience; SEC pushes for lower end |
| Legal documents | Grade 12-14 | 20-35 | Precision language required; plain-language movement improving this |
| Academic papers | Grade 14-18 | 10-30 | Peer audience; complex concepts require specialized vocabulary |
Notable reference points: Hemingway wrote at grade level 5. The IRS tax instructions average grade 12. The typical insurance policy is grade 15. The U.S. Constitution is grade 17.8.
10 Proven Tips to Improve Text Readability
Shorten Your Sentences
Keep sentences under 20 words on average. Research shows that sentences of 8 words are understood by 100% of readers, while sentences of 28 words drop to 77%. Break compound sentences at conjunctions. Use one idea per sentence. Vary length for rhythm, but monitor the average.
Replace Complex Words With Simpler Alternatives
Every readability formula penalizes multi-syllable words. Swap "utilize" for "use," "approximately" for "about," "facilitate" for "help," "commence" for "start," and "terminate" for "end." The simple word is almost always the better word.
Use Active Voice
Passive voice adds words and obscures agency. "The report was written by the team" (8 words, passive) becomes "The team wrote the report" (6 words, active). Active voice is shorter, clearer, and more engaging. Aim for 90%+ active voice.
Break Up Long Paragraphs
Limit paragraphs to 3-4 sentences or about 75 words. On screens, dense blocks of text cause readers to skim or leave. Add descriptive subheadings every 200-300 words to create entry points and improve scannability.
Cut Filler Words
Remove "very," "really," "just," "quite," "rather," "somewhat," "basically," "actually," "literally," "definitely," and "honestly." These words add syllables and sentence length without adding meaning. Run a search-and-review for each one in your draft.
Add Transition Words
Transitions guide the reader between ideas. Use "however," "therefore," "for example," "in addition," "as a result," "meanwhile," and "specifically." They improve flow and comprehension without significantly increasing complexity scores.
Use Lists and Bullet Points
Convert any series of three or more items from paragraph form into a bulleted or numbered list. Lists reduce sentence length, improve scannability, and make information easier to remember. Use numbered lists for sequential steps, bullets for unordered items.
Define Jargon on First Use
If a technical term is necessary, define it immediately: "The API (Application Programming Interface) allows two programs to communicate." After defining it once, use the abbreviation. If the term is not necessary, replace it with a plain-language alternative.
Read Your Text Aloud
If you stumble while reading, your reader will too. Spoken language naturally trends toward shorter sentences and simpler words. Reading aloud exposes awkward phrasing, unnecessary complexity, and overly long sentences that look fine on screen but fail in speech.
Test With a Readability Analyzer
After revising, paste your text into a readability score checker to verify improvement. Compare Flesch, Gunning Fog, and SMOG scores before and after. Target the benchmark for your audience. Iterate until scores align with your goal.
Before & After: Readability Rewrites
Theory is useful, but examples are better. Here are three real-world passages rewritten for improved readability, with scores for each version.
Example 1: Healthcare Communication
Patients presenting with symptomatology consistent with acute myocardial infarction should be administered aspirin in a dosage of 325 milligrams via the oral route unless contraindicated by a documented history of aspirin hypersensitivity or active gastrointestinal hemorrhage.
If you think you are having a heart attack, chew one regular aspirin (325 mg) right away. Do not take aspirin if you are allergic to it or if you have stomach bleeding.
Example 2: Software Documentation
The implementation necessitates the utilization of an asynchronous methodology for the initialization of the database connection, subsequently facilitating the execution of parameterized queries to mitigate the vulnerability surface associated with SQL injection attack vectors.
Connect to the database using an async function. Use parameterized queries to prevent SQL injection attacks.
Example 3: Legal/Terms of Service
Notwithstanding any provision herein to the contrary, the indemnifying party shall hold harmless and indemnify the indemnified party from and against any and all claims, damages, losses, costs, and expenses, including but not limited to reasonable attorneys' fees, arising out of or in connection with any breach of the representations and warranties set forth herein.
If one party breaks a promise in this agreement, that party must pay for any resulting losses. This includes the other party's legal fees.
In each case, the rewritten version conveys the same essential meaning at a fraction of the reading difficulty. The key techniques: shorter sentences, simpler words, active voice, and removal of legal/technical filler.
Writing for Different Audiences
General Public (Grade 6-8)
When writing for a general audience, assume no specialized knowledge. Use everyday words. Keep sentences short. Define any term that a high-school freshman might not know. This is the standard for most web content, marketing materials, news articles, and government communications. The Plain Writing Act of 2010 requires federal agencies to use this standard.
Professionals in a Specific Field (Grade 8-12)
For audiences with domain expertise, you can use field-specific terminology without defining every term. A software developer understands "API endpoint." A physician understands "bilateral pneumonia." The key is to keep sentence structure simple even when vocabulary is specialized. Technical vocabulary is acceptable; convoluted syntax is not.
Academic and Scientific Audiences (Grade 12+)
Academic writing serves a unique function: precision of argument and reference to prior work. Higher grade levels are sometimes unavoidable. However, the best academic writers still aim for clarity within the constraints of their discipline. Short sentences remain more effective than long ones, even in a PhD thesis. The trend in scientific publishing is toward plainer language, with journals like Nature and Science actively editing for readability.
Children and Young Readers (Grade 1-5)
Writing for children requires more than simple vocabulary. Sentences should be 5-10 words. Use concrete nouns and action verbs. Avoid abstractions. Repeat key words instead of using pronouns. Every sentence should advance the story or idea. Dr. Seuss wrote "Green Eggs and Ham" using only 50 unique words.
Non-Native English Speakers
For international audiences, target grade 6 or below. Avoid idioms ("break the ice," "back to the drawing board"), phrasal verbs ("figure out," "come up with"), and cultural references. Use standard English sentence structures. Short, declarative sentences translate better. The Special English standard developed by Voice of America uses a 1,500-word vocabulary at a grade 5 level.
Check Your Text Now
Paste your content into Enhio's free readability analyzer for instant Flesch, Gunning Fog, and SMOG scores.
Open the Readability ToolFrequently Asked Questions
What is a good readability score?
For general web content, aim for a Flesch Reading Ease score of 60-70 and a Flesch-Kincaid Grade Level of 7-8. This reaches the widest English-speaking audience. Medical content should target grade 6. Academic writing may legitimately reach grade 12 or higher.
How do I improve my Flesch Reading Ease score?
The Flesch formula has two inputs: average sentence length and average syllables per word. To raise your score, shorten sentences (split at conjunctions, remove subordinate clauses) and replace long words with short ones (use instead of utilize, help instead of facilitate). Every syllable you remove increases the score.
What is the difference between Flesch Reading Ease and Flesch-Kincaid Grade Level?
Both use the same inputs but produce opposite scales. Reading Ease gives a 0-100 score where higher means easier. Grade Level maps to a U.S. school grade where lower means easier. A Reading Ease of 60 roughly corresponds to a Grade Level of 8-9. They always move in opposite directions.
Which readability formula is best?
No single formula is universally best. Use Flesch-Kincaid for general content. Use SMOG for health materials (it estimates 100% comprehension). Use Coleman-Liau or ARI for automated pipelines (they avoid syllable counting). Use Gunning Fog for business writing. When in doubt, use all six and look at the consensus.
Can readability scores be too low?
Yes. If your grade level drops below 4-5 for adult audiences, the text may feel patronizing or lack necessary nuance. A patent application requires precise legal language. A medical journal article requires exact scientific terminology. The goal is to match readability to your audience, not to minimize the score unconditionally.
How many words should a sentence have for good readability?
Aim for an average of 15-20 words per sentence. Sentences under 14 words are understood by 90% of readers. Sentences over 40 words are understood by only 10%. Mix short sentences (5-10 words) with medium ones (15-20 words) for natural rhythm. Reserve sentences over 25 words for rare, necessary occasions.