Flesch-Kincaid Grade Level Calculator
Readability tools translate the feel of a piece of writing into a single, comparable number, and the Flesch-Kincaid grade level is the most widely used of them. It estimates the US school grade a reader would need to follow your text, so a score of 8 suggests an average eighth grader could read it comfortably. This calculator computes that grade from three counts you supply: the total words, the total sentences and the total syllables in your sample. The formula blends two ideas about what makes text hard, longer sentences and longer words. It multiplies the average words per sentence by 0.39, adds 11.8 times the average syllables per word, and subtracts the constant 15.59, all of which come from the original Kincaid research. Lower scores mean easier reading. General web writing often aims for grade 7 to 9, and plain-language public guidance frequently targets grade 6 to 8, while technical and academic writing runs higher and is not capped, so dense prose can score into college levels. Treat the result as a guide to where shorter sentences or simpler words would help, not a rigid rule. Every figure here is computed deterministically from your three counts, and the worked example below reconciles exactly to the calculator.
The grade is 0.39 x (words/sentences) + 11.8 x (syllables/words) - 15.59. A sample of 120 words, 6 sentences and 180 syllables scores about grade 9.91.
Flesch-Kincaid grade formula
grade = 0.39 x (W / S) + 11.8 x (Y / W) - 15.59
W = total words
S = total sentences
Y = total syllables
The first term grows with sentence length and the second with word length, so longer sentences and longer words both push the grade up. The constant shifts the result onto the US grade scale.
Worked example
A passage has 120 words, 6 sentences and 180 syllables.
- Words per sentence: 120 / 6 = 20
- Syllables per word: 180 / 120 = 1.5
- Grade: 0.39 x 20 + 11.8 x 1.5 - 15.59 = 7.8 + 17.7 - 15.59 = 9.91
The text scores about grade 9.91, roughly a high-school reading level. These are the calculator's default inputs, so the result above matches the widget exactly.
Grade level guidance
| Grade score | Typical reader |
|---|---|
| 5 to 6 | Easy, broad public |
| 7 to 9 | General web writing |
| 10 to 12 | High school |
| 13 and up | College and beyond |
Measurement and information standards: US National Institute of Standards and Technology (NIST).
Flesch-Kincaid grade calculator: frequently asked questions
What is the Flesch-Kincaid grade level?
It is a readability score that estimates the US school grade needed to understand a text. A score of 8 means an average eighth grader could read it. The formula combines average sentence length and average syllables per word into a single grade number, so lower scores mean easier reading.
What is the Flesch-Kincaid grade formula?
Grade equals 0.39 times words per sentence, plus 11.8 times syllables per word, minus 15.59. Words per sentence is total words divided by sentences, and syllables per word is total syllables divided by words. The three constants come from the original Kincaid study.
What grade level should I aim for?
General audience web writing often targets grade 7 to 9, which is clear without being childish. Plain-language government guidance frequently aims for grade 6 to 8. Technical or academic writing runs higher. The right target depends on your readers, so use the score as guidance rather than a strict rule.
How do I count syllables and sentences?
Count a sentence at each period, question mark or exclamation mark. Count syllables by the vowel sounds you hear when you say each word aloud. Many tools count these automatically, but the formula itself just needs the totals, which is why this calculator asks for the three counts directly.
Why can the score be higher than grade 12?
The formula is not capped, so dense writing with long sentences and many multi-syllable words can score above 12, into college and postgraduate levels. A very high score is a signal to shorten sentences and choose simpler words if you want a broader audience.
Official sources
- Measurement and information standards: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.