Flesch Reading Ease and Flesch-Kincaid Grade Level: Formulas and a Worked Example
October 29, 2026
Readability formulas estimate how difficult a text is to read, based on sentence length and word length. The most common are the Flesch Reading Ease score and the Flesch-Kincaid Grade Level. Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). Higher scores mean easier text. Grade Level = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59, giving the approximate US school grade needed to understand the text.
For a passage of 100 words in 5 sentences with 150 syllables: words per sentence = 20 and syllables per word = 1.5. Reading Ease = 206.835 − 1.015 × 20 − 84.6 × 1.5 = 206.835 − 20.3 − 126.9 = 59.6. Grade Level = 0.39 × 20 + 11.8 × 1.5 − 15.59 = 7.8 + 17.7 − 15.59 = 9.9.
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Reading Ease scores are interpreted as follows: 90 to 100 very easy (5th grade); 80 to 90 easy (6th grade); 70 to 80 fairly easy (7th grade); 60 to 70 plain English (8th and 9th grade); 50 to 60 fairly difficult (10th to 12th grade); 30 to 50 difficult (college); 0 to 30 very difficult (college graduate). Our passage, at 59.6, is borderline between plain English and fairly difficult. General audience writing, such as news and marketing, often targets a score of 60 to 70; legal, medical, and technical writing frequently scores below 40. Many government plain-language guidelines recommend writing at an eighth-grade level or lower for public documents.
| Flesch Reading Ease | Difficulty | Typical US grade | Example |
|---|---|---|---|
| 90 to 100 | Very easy | 5th | Children's stories |
| 70 to 80 | Fairly easy | 7th | Popular fiction |
| 60 to 70 | Plain English | 8th to 9th | Newspapers |
| 30 to 50 | Difficult | College | Academic papers |
| 0 to 30 | Very difficult | Graduate | Legal contracts |
Worked Comparison
Take a second passage: 120 words in 8 sentences, with 150 syllables. Words per sentence = 15, syllables per word = 1.25. Reading Ease = 206.835 − 1.015 × 15 − 84.6 × 1.25 = 206.835 − 15.2 − 105.75 = 85.9: easy. Grade Level = 0.39 × 15 + 11.8 × 1.25 − 15.59 = 5.85 + 14.75 − 15.59 = 5.0. The second passage uses shorter sentences and shorter words, resulting in much easier text. Splitting a 20-word sentence into two 10-word sentences would raise the score by about 10 points; replacing 'utilize' with 'use' lowers the syllable count.
How to Improve Readability
Use shorter sentences, aiming for an average of 15 to 20 words. Choose plain words: 'use' for 'utilize', 'start' for 'commence'. Prefer active voice. Break text into short paragraphs, use headings and bullet lists, and define technical terms. Read your text aloud and cut anything that makes you stumble. Do not make the text too simple for the audience or the topic: a score is a guide, not a goal. Word processors include readability statistics in their spelling and grammar tools.
Limits
Formulas ignore vocabulary familiarity, sentence structure, organization, and the reader's background. A text full of short words can still be confusing, and a technical term with many syllables might be familiar to specialists. Counting syllables automatically is imperfect. Languages other than English need different formulas (e.g., Flesch-Douma for Dutch, Fernández Huerta for Spanish). Use readability scores along with testing with real readers.
Frequently Asked Questions
What is the Flesch Reading Ease formula?
206.835 − 1.015 × (words per sentence) − 84.6 × (syllables per word).
What is a good Flesch Reading Ease score?
60 to 70 is considered plain English suitable for most readers.
What does grade level mean?
The approximate US school grade needed to understand the text.
How can I raise the score?
Shorten sentences and use shorter, simpler words.
Do readability scores apply to other languages?
Not directly. Each language has its own adapted formulas.