When Should I Use Readability Formulas and When Should I Not?

Readability formulas are tools that analyze the readability of text, usually by calculating sentence length, word length, and syllables. Most formulas output several statistics, such as a score that correlates with a reader’s grade or reading level. This number, along with other pertinent information, can help writers craft content that matches their intended audience. You can use these formulas on most types of texts, but not all.

When to Use Readability Formulas

✓ Educational Content. When you need to match grade-appropriate textbooks and educational content to the reading level of students, use readability formulas to help with this task. Most schools in the U.S. use one or more formulas to score or procure grade-appropriate learning materials.

✓ Health Communications. Readability formulas can help create easy-to-understand materials for the general population. Patient information leaflets, consent forms, and public health notices must be accessible to people with varying literacy levels. The Centers for Disease Control and Prevention (CDC) suggests that health information be written two levels below the population’s average grade reading level, which corresponds to a 6th-grade reading level. For individuals over 65, the agency suggests an even lower reading level​.

✓ Legal Documents. Making policies, laws, and regulations comprehensible to non-specialists is crucial. Using these formulas can help simplify complex texts without oversimplifying the content. The U.S. Department of Health & Human Services (HHS) emphasizes that plain writing is mandated by law and counters the myth that content must be “dumbed down” for plain language. Instead, the focus is on clear communication—accessible to the audience.

✓ Publishing Industry. Editors and publishers use readability scores to determine if a text is appropriate for their target audience. This is especially true for children’s literature and materials for English language learners. According to The Publishers Association, “In an increasingly competitive publishing landscape, readability metrics can help tailor content to meet the diverse needs of readers, improving reader engagement.”

✓ News Articles. In constantly-changing environments, journalists and reporters gather and translate complex information and write their articles that favors accessibility for the general public. Readability formulas help these professionals use simple language, with straightforward sentences and common, high-frequency words. This style is especially important when they report on critical updates affecting how communities react and stay safe. The Associated Press Stylebook advises journalists to use short words and sentences to improve readability, as this style resonates better with a wider audience.

✓ Web Content. With the vast range of literacy levels among Internet users, web content creators can use readability formulas to ensure their information is accessible to a wider audience. According to the World Wide Web Consortium (W3C), “Web accessibility is a fundamental right…regardless of their literacy levels.”

✓ User Manuals/Instructions. For products that will reach a diverse consumer audience, customers need to follow installation instructions despite lacking technical know-how. Readability formulas can help technical writers craft clear how-to instructions. “Over 60% of product-related accidents are due to unclear or poorly written instructions. Readability assessments are key to mitigating these risks,” according the International Journal of Industrial Ergonomics.

✓ Business Communications. In the corporate world, clarity is key. Whether it’s memos, reports, or emails, readability formulas can help professionals communicate more effectively with their colleagues. The Corporate Leadership Council reports that “Companies that prioritize clear and readable communication experience a 30% increase in employee engagement and a 25% improvement in decision-making processes.”

✓ Advertising Copy. Readability formulas can help copywriters craft messages that are easy to read at a glance, making them more likely to capture the attention of potential customers. A study by the Nielsen Company found that: “Ads with higher readability scores are 50% more likely to be noticed and recalled by viewers, increasing brand recognition and purchase intent.”

✓ Social Media. With the rapid scrolling culture of social media, posts with higher readability are more likely to engage a broader audience. These formulas can guide content creators in crafting digestible messages. “Clear and accessible messages are more likely to influence behavior and opinions in the online social sphere,” according to The American Psychological Association (APA).

✓ Grant Writing. When seeking funding, it’s crucial that the proposal is clear to all reviewers. Readability formulas can help refine the language so that the key points are communicated effectively.

✓ Public Speaking. Speakers can use readability formulas to assess their speech scripts, ensuring their audience can understand their message easily.

When Not to Rely on Readability Formulas

✗ Nuanced or Creative Writing. Literature, poetry, and certain forms of creative non-fiction often play with language in ways that are intentionally complex or challenging. Readability formulas do not account for stylistic choices or the artistic merit of text.

✗ Technical or Specialist Texts. Academic papers, technical manuals, and industry-specific reports are meant for specialized audiences familiar with the jargon and complex ideas. Not all formulas will accurately score the appropriateness of these texts. For advanced and technical texts, users can use the FORCAST Formula.

✗ Cultural Sensitivity.  Because these formulas are based on syntactic and lexical measures, they do not consider cultural references, idioms, or regional language variations—these can be important in multicultural or multilingual contexts.

✗ Audience Engagement. Sometimes the goal of a text is to engage readers more deeply with the content. A higher readability score may not reflect the text’s engagement.

✗ Marketing Materials. These often aim for impact, brevity, and memorability rather than adherence to readability standards. Slogans, for instance, may not conform to readability standards but are effective in their context.

✗ Cultural Literature/Folklore. These texts are often rich in cultural expressions and linguistic nuances that readability formulas cannot account for. The educational value and cultural significance lie beyond the scope of what readability scores can measure.

✗ Satire and Irony. Satirical writing or irony often hinges on language and the double meanings that readability formulas would likely misinterpret as complexity rather than stylistic devices.

✗ Poetry/Abstract Writing. Poetry and certain forms of abstract prose deliberately flout conventional syntax and vocabulary to evoke emotions or sensory effects, which readability formulas are not equipped to appreciate.

✗ Dialogue Texts. Plays, scripts, and novels that feature a lot of dialogue may mislead readability scores because the spoken language is often more colloquial and fragmented than formal prose.

✗ Persuasive Texts. Political speeches, opinion pieces, and advocacy materials are crafted to persuade and may use rhetorical devices that are not quantifiable by readability metrics but are central to the text’s effectiveness.

✗ Transcribed Speeches/Interviews. The informal and spontaneous nature of spoken language does not always translate into high readability scores, despite being easily understood in its spoken form.

✗ Slang and Jargon. Texts that appeal to specific groups or subcultures through slang, technical jargon, or insider language may score less readable, yet they communicate effectively within their target group.

✗ Experimental Writing. Some authors may experiment with language and structure to challenge readers or to convey complex themes and ideas that readability formulas are not designed to capture.

✗ Historical Texts. The language in historical documents often contains archaic vocabulary and syntax that readability formulas may score as complex, even though such texts are crucial for understanding history and culture.

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