Flesch-Kincaid grade level and Flesch Reading Ease, computed live as you type
| Score | Reading Level | Typical Writing |
|---|---|---|
| 90-100 | 5th grade | Very easy: children's books, greeting cards |
| 80-90 | 6th grade | Easy: digest magazines, popular fiction |
| 70-80 | 7th grade | Fairly easy: consumer magazines |
| 60-70 | 8th-9th grade | Plain English: newspapers, most web copy |
| 50-60 | 10th-12th grade | Fairly difficult: trade journals, quality magazines |
| 30-50 | College | Difficult: academic papers, professional journals |
| 0-30 | College graduate | Very difficult: legal, academic, government prose |
Higher is easier. Microsoft Word's readability report, Hemingway, and readabilityWP all use these same bands.
| Content Type | Typical Reading Ease | Typical FK Grade |
|---|---|---|
| Marketing copy and ads | 70-90 | 4-7 |
| News and general blog posts | 60-70 | 7-9 |
| Technical documentation | 45-60 | 9-12 |
| Academic journal articles | 10-40 | 13-18 |
| Legal contracts and statutes | 0-30 | 14-20+ |
Commonly cited approximations from published readability studies; individual documents vary widely within each genre.
Flesch-Kincaid compresses a passage into two numbers, average sentence length and average syllables per word, and maps them to a US school grade. Short sentences of short words score easy; long sentences of long words score hard. That's the whole model, and its bluntness is a feature: it's reproducible, and it tells you exactly which dial to turn.
Flesch-Kincaid Grade Level = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59. The result reads as a grade: 8.0 means an average 8th grader handles it.
Flesch Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). This is the older companion (Flesch, 1948) scored 0-100 where higher is easier; Kincaid's 1975 adaptation for the US Navy produced the grade-level version.
Syllables are counted with the standard vowel-group heuristic: strip to letters, count groups of consecutive vowels, drop silent trailing e, minimum one per word.
Take a deliberately easy sentence: "The quick brown fox jumps over the lazy dog." Nine words, one sentence, eleven syllables. Words per sentence = 9; syllables per word = 11 ÷ 9 = 1.22.
Reading Ease = 206.835 − 1.015 × 9 − 84.6 × 1.22 = 206.835 − 9.135 − 103.4 = 94.3, very easy, 5th grade. FK Grade = 0.39 × 9 + 11.8 × 1.22 − 15.59 = 3.51 + 14.42 − 15.59 = 2.3.
Now the hard one: "Payment of the full balance remains due within thirty days of receipt, and late submissions may incur additional penalties pursuant to the applicable regulations." Twenty-four words, one sentence, forty-five syllables. Syllables per word = 1.875. Reading Ease = 206.835 − 24.36 − 158.63 = 23.9, college-graduate territory. FK Grade = 9.36 + 22.13 − 15.59 = 15.9. Same formula, and the gap between the two passages shows up in the score exactly the way it feels on the page.
Split long sentences: every sentence cut in half drops the average by its own length. Swap polysyllables: "utilize" for "use" costs 2 syllables per occurrence. And keep the reader's real level in mind; plain-English targets exist to widen reach, not to flatten every document to 6th grade.
For general audiences, a Flesch Reading Ease between 60 and 70, which maps to roughly 8th-9th grade on the Flesch-Kincaid Grade Level scale. Web copy and marketing often aim for 60-80 (grades 6-9), technical documentation for 50-60, and academic or legal writing commonly lands at 30 or below. Match the score to the reader, not to a universal target: a 40 is wrong for a blog post and right for a law review.
FK Grade = 0.39 x (words per sentence) + 11.8 x (syllables per word) - 15.59. The companion Flesch Reading Ease score is 206.835 - 1.015 x (words per sentence) - 84.6 x (syllables per word). Both use the same two inputs: average sentence length and average syllables per word, counted with the standard vowel-group heuristic.
It means roughly 8th-9th grade reading level: plain English understood by most high school graduates. The scale runs 0-100, where higher is easier. 70-80 is 7th grade, 60-70 is 8th-9th, 50-60 is 10th-12th, 30-50 is college level, and below 30 is college-graduate level.
Because both formulas reward exactly those two things. Halving average sentence length drops the FK grade quickly, and swapping polysyllabic words (utilize, approximately) for short ones (use, about) cuts the syllables-per-word term. It's arithmetic, not judgment: the formula can't tell a well-structured long sentence from a rambling one.
The standard vowel-group heuristic counts groups of consecutive vowels, with adjustments for silent e endings and short words. It's right for the large majority of common English words but stumbles on words like 'business' or 'beautiful' where vowels don't split cleanly. Word's built-in checker uses the same approach, so scores match published tools within a point or two on typical prose.
Not reliably. The constants in both formulas were fitted to English prose (Flesch 1948; Kincaid's 1975 adaptation for the US Navy). Other languages have their own readability formulas: LIX for Scandinavian languages, Fernández-Huerta for Spanish, Amstad for Portuguese. Running German or French text through Flesch produces misleading numbers.