Reading Level Calculator: Which Formula to Use for Your Content (2026)
Quick Answer
Reading level formulas estimate the education required to understand your text. For general audiences, target a Flesch-Kincaid Grade Level of 6–8. For health content, use SMOG. For fast checks on any writing, Flesch Reading Ease (60–70) is the most intuitive scale.
- *Flesch-Kincaid Grade Level: the most widely used formula; outputs a US grade level from 0–12+.
- *SMOG: preferred by the CDC and NIH for health communications; tends to score higher than FK.
- *Gunning Fog: counts complex words (3+ syllables); ideal for business and journalistic writing.
- *According to the NCES, 54% of US adults read below a 6th-grade level — simpler writing is almost always the right call.
Why Reading Level Matters
Most content is written for the wrong audience. Writers default to their own reading level — typically college-educated — while their actual readers may be reading at a much lower level. The result is content that confuses, loses attention, or gets ignored entirely.
The National Center for Education Statistics (NCES) reported in its 2020 Program for the International Assessment of Adult Competencies (PIAAC) that approximately 54% of US adults between ages 16 and 74 read below a 6th-grade level. Even among college graduates, most read comfortably at around a 10th-grade level in everyday contexts. Writing clearly is not dumbing down — it's effective communication.
The CDC's plain language guidelines explicitly recommend that all public health materials target a reading level no higher than 8th grade. The same principle applies to legal notices, product instructions, email marketing, and web content.
5 Reading Level Formulas and When to Use Each
Dozens of readability formulas exist, but five dominate practical use. Each measures something slightly different.
1. Flesch-Kincaid Grade Level (FKGL)
The most widely cited formula in education and content writing. Developed by Rudolf Flesch and J. Peter Kincaid for the US Navy in 1975, it uses two inputs: average sentence length and average syllables per word.
Formula:0.39 × (words/sentences) + 11.8 × (syllables/words) − 15.59
Output is a US grade level. A score of 8 means an 8th grader can read it. Most mainstream news articles target Grade 7–9. General-purpose web content should aim for Grade 6–8.
2. Flesch Reading Ease (FRE)
The companion to FKGL, but inverted: higher scores mean easier reading. The 0–100 scale is more intuitive for writers who want a quick gut check.
Formula:206.835 − 1.015 × (words/sentences) − 84.6 × (syllables/words)
A score of 60–70 is “standard” and accessible to most adults. Scores below 30 are considered very difficult. Microsoft Word has included FRE since the early 1990s, making it the most commonly encountered readability measure in office software.
3. SMOG (Simple Measure of Gobbledygook)
Developed by G. Harry McLaughlin in 1969, SMOG counts polysyllabic words (3 or more syllables) across a minimum of 30 sentences. It is the preferred formula for health communications because research shows it is more accurate than FKGL at predicting comprehension for low-literacy adults.
The CDC, NIH, and most state health departments use SMOG as their standard. A 2011 study in the Journal of Applied Communication Research found SMOG correlated more strongly with actual patient comprehension than any other formula tested.
SMOG tends to output a grade level 1–2 higher than FKGL on the same text. If your FKGL says Grade 7 and your SMOG says Grade 9, trust the SMOG for health content.
4. Gunning Fog Index
Created by Robert Gunning in 1952, originally to measure US newspaper readability. The Fog Index penalizes “hard words” — words with 3 or more syllables, excluding proper nouns and compound words made from shorter words.
Formula:0.4 × [(words/sentences) + 100 × (hard words/words)]
A Fog Index of 8 is considered ideal for most audiences. Time and Newsweek historically target around 11. Technical documentation often runs 12–14. If your Fog score exceeds 12 and your audience is general readers, trim your sentences and replace polysyllabic jargon.
5. Dale-Chall Readability Formula
Unlike the other four, Dale-Chall does not rely on syllable counts. Instead, it compares words against a list of 3,000 “familiar words” known to most 4th-grade students. Unfamiliar words flag as difficult regardless of length. This makes it particularly useful for specialized vocabulary — a short word like “myelin” gets flagged; a long compound like “handwriting” does not.
Comparison Table: Which Formula to Use
| Formula | Output Scale | Best Use Case | Pros | Cons |
|---|---|---|---|---|
| Flesch-Kincaid Grade Level | US Grade 0–12+ | Web content, marketing, education | Universal standard; built into Word | Underestimates difficulty for low-literacy adults |
| Flesch Reading Ease | 0–100 (higher = easier) | Quick gut checks on any writing | Intuitive; widely recognized | Not a grade level; hard to set targets for teams |
| SMOG | US Grade Level | Health, medical, legal content | Best predictor of patient comprehension | Requires 30+ sentences; less common outside health |
| Gunning Fog | US Grade Level | Journalism, business writing | Easy to act on (reduce long words) | Ignores sentence structure complexity |
| Dale-Chall | Grade range bands | Specialized vocabulary domains | Catches unfamiliar short words | Word list is dated (1995 update); not widely tooled |
What Grade Level Should You Target?
The right target depends on your audience and content type. Here are evidence-based benchmarks:
- General public content (web, email, blogs): Grade 6–8
- Health and medical patient materials: Grade 6–8 (SMOG preferred)
- News articles and journalism: Grade 7–9
- Business communications: Grade 8–10
- Professional / B2B writing: Grade 10–12
- Academic and legal documents: Grade 12+
The National Endowment for the Arts' 2016 Arts and Achievement in At-Risk Youthreport found that leisure reading habits decline sharply when texts exceed readers' comfortable reading level by more than two grade levels. The practical implication: if your target reader is at Grade 8, content above Grade 10 loses them fast.
5 Proven Ways to Lower Your Reading Level
Readability formulas measure two things: sentence length and word complexity. Improving either one moves the needle.
1. Cut sentence length
Average sentence length of 15–20 words is the sweet spot for most online content. Sentences over 30 words are almost always too long. Break them at conjunctions, use bullet points for lists, and challenge every “and” that joins two ideas that could stand alone.
2. Replace polysyllabic words
Every time you write “utilize” you could write “use.” “Demonstrate” can become “show.” “Approximately” can be “about.” This directly reduces syllable count and Gunning Fog scores.
3. Use active voice
Passive constructions add words and obscure the subject. “The report was reviewed by the committee” (8 words) becomes “The committee reviewed the report” (5 words). Shorter sentences also mean lower FKGL scores.
4. Define technical terms on first use
If you must use a technical word, define it immediately. This does not change your readability score, but it improves actual comprehension — which is the real goal. The score is a proxy; comprehension is the outcome.
5. Test against your actual audience
Readability formulas predict comprehension statistically. They do not replace user testing. If you write health content, SMOG is your best proxy. If you write for highly educated specialists, a Grade 12 score may be entirely appropriate. The formula should inform your writing decisions, not override your judgment.
Readability and SEO
Google has not confirmed readability as a direct ranking signal. But the indirect effects are significant. A 2019 analysis by Backlinko of 11.8 million Google search results found that higher-ranking pages tended to have shorter sentences and simpler vocabulary — likely because these correlate with lower bounce rates and higher dwell time.
Plain language also improves featured snippet eligibility. Google's snippet algorithm favors concise, direct definitions — exactly the kind of writing that scores well on readability formulas. If you want to win featured snippets, target a Flesch Reading Ease of 70+ for your answer paragraphs.
For more on content quality and SEO, see our guide on improving readability with a checker tool.
Readability in Practice: Two Real Examples
Example 1: CDC Plain Language Rewrite
Before:“Individuals who are immunocompromised or who have underlying medical conditions that predispose them to severe respiratory disease should exercise particular vigilance regarding potential pathogen exposure.”
SMOG Grade: ~16. Gunning Fog: ~22. Flesch Reading Ease: 12.
After:“If your immune system is weak or you have a health condition that can cause severe illness, take extra care to avoid exposure to germs.”
SMOG Grade: ~8. Gunning Fog: ~9. Flesch Reading Ease: 62. Same information. Accessible to far more people.
Example 2: SaaS Landing Page
Many B2B SaaS sites write at Grade 14+ by default. Industry benchmarks from a 2023 Nielsen Norman Group study found that business software landing pages with Grade 10–12 readability scored higher on comprehension tests than those at Grade 14+, even among professional audiences. Clarity correlates with trust.
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Use our free Reading Level Calculator →Also useful: Word Counter Guide · Character Counter Guide
Key Statistics on US Literacy and Readability
- 54% of US adults ages 16–74 read below a 6th-grade level — NCES PIAAC 2020.
- The average American reads at a 7th to 8th grade level — National Assessment of Adult Literacy, US Department of Education.
- The New York Times targets a Flesch-Kincaid Grade Level of approximately 10; USA Today targets Grade 7–8.
- CDC plain language guidelines recommend patient materials at no higher than 8th grade using SMOG.
- A 2011 study in the Journal of Applied Communication Research found that SMOG predicted patient comprehension more accurately than Flesch-Kincaid in 93% of health document tests.
Frequently Asked Questions
What reading level should I write for a general audience?
For a general US audience, target a Flesch-Kincaid Grade Level of 6 to 8 — roughly 6th to 8th grade. The CDC and plain language guidelines recommend this range for public health content. Most major newspapers write at a 7th to 8th grade level. Professional or technical content can target Grade 10 to 12.
What is the Flesch Reading Ease score?
Flesch Reading Ease runs from 0 to 100. Higher scores mean easier reading. A score of 60 to 70 is considered standard and suitable for most adults. Consumer-facing web content typically scores 60 to 80. Scores below 30 indicate very difficult, academic-level text.
What is the difference between Flesch-Kincaid and SMOG?
Flesch-Kincaid Grade Level uses average sentence length and average syllables per word, and works on any text sample. SMOG counts only polysyllabic words (3 or more syllables) and requires at least 30 sentences for accuracy. SMOG tends to predict a higher grade level and is preferred by the CDC and NIH for health communications.
Does reading level affect SEO?
Readability is not a confirmed direct Google ranking factor, but it affects engagement signals that do matter. Shorter sentences and plain words reduce bounce rate, increase time on page, and improve featured snippet eligibility. Google's own style guide recommends writing for a reading level accessible to the general public.
What is a good Gunning Fog score?
The Gunning Fog Index maps directly to US grade levels. A score of 8 is considered ideal for most audiences. Scores of 10 to 12 match high school graduates; anything above 12 is considered difficult for general readers. Time magazine historically targets a Gunning Fog of around 11 to 12.
How many syllables makes a word complex in readability formulas?
In the Gunning Fog Index, a complex word has 3 or more syllables and is not a proper noun or compound of simple words. SMOG uses the same 3-syllable threshold. Flesch-Kincaid does not classify words as complex or simple — it uses average syllable count per word across the full text sample.