Flesch-Kincaid Grade Level calculator

Paste your text to see its Flesch-Kincaid Grade Level — the US school grade a reader needs to follow it — plus the reading age, the calculation, and every other major readability score. Free, and your text stays in your browser.

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The Flesch-Kincaid Grade Level formula

Grade Level = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59

Words ÷ sentences — average sentence length. Ten extra words per sentence adds about four grades.
Syllables ÷ words — average word length. Each extra tenth of a syllable per word adds more than a grade.
The result — a US school grade. Add five for a rough reading age: grade 3 suits most 8-year-olds.

Worked example

Here is the Flesch-Kincaid Grade Level worked through for our sample bedtime story — press Try a sample story above to load it. It’s a short tale about an owl who can’t sleep, and it counts up like this:

Words: 118
Sentences: 18
Syllables: 141

0.39 × (118 ÷ 18) + 11.8 × (141 ÷ 118) − 15.59 = 1.1

So the story scores 1.1 — Grade 1 · ages 6–7.

What your score means

Score	Level	Who reads it easily
1 or below	Kindergarten–1st grade	Ages 5–7 · picture books, first readers
2–3	2nd–3rd grade	Ages 7–9 · early chapter books
4–5	4th–5th grade	Ages 9–11 · confident young readers
6–8	Middle school	Ages 11–14 · most adults read this comfortably
9–12	High school	Ages 14–18 · news features, business writing
13–16	College	Academic and specialist writing
17+	Graduate	Dense professional or scientific prose

What is a good Flesch-Kincaid Grade Level?

For a general adult audience, aim for grade 8 or below — around the level of a popular newspaper feature. Public-sector plain-language guidance and most health-literacy advice push lower still, to grades 6–8, because plenty of adults read most comfortably there.

For children, match the grade to the reader. A book a child reads alone should sit at or just below their school grade; a story you read aloud can comfortably be a grade or two higher, because children understand more than they can decode.

Where it comes from

In 1975 J. Peter Kincaid and colleagues, working for the US Navy, recalculated Rudolf Flesch’s 1948 Reading Ease formula so it would output a school grade instead of a 0–100 score. They tested it on enlisted personnel reading technical training material.

The US military went on to use it as a standard for technical manuals, and it spread from there: Microsoft Word reports it, and it’s probably the most quoted readability score in education and publishing.

Limitations

The grade is an estimate from two averages — sentence length and word length. It can’t see whether vocabulary is familiar, whether ideas are abstract, or whether the story itself suits a child’s age.

Very simple text produces grades below zero, which just means “easier than kindergarten level”. And because every tool estimates syllables slightly differently, the same text can come out a few tenths of a grade apart in different checkers.

How to calculate Flesch-Kincaid Grade Level by hand

Take a passage of at least 100 words and count its words, sentences and syllables. Divide words by sentences for the average sentence length, and syllables by words for the average syllables per word.

Multiply the sentence length by 0.39 and the syllables per word by 11.8, add them, and subtract 15.59. The answer is a US school grade.

What lowers the grade fastest

Each word you take off the average sentence lowers the grade by 0.39, so trimming five words from a typical sentence drops it by about two grades.

Word length matters more per unit. Moving from 1.5 to 1.3 syllables per word — swapping a few “remember”s for “know”s — lowers the grade by about 2.4. In children’s writing, where sentences are already short, simpler words are usually the bigger lever.

Our sample bedtime story averages 6.6 words a sentence and 1.19 syllables a word, which is why it scores just 1.1.

Frequently asked questions

What does a Flesch-Kincaid Grade Level of 8 mean?

That a typical US 8th grader — around age 13 to 14 — could understand the text. It’s a common target for writing aimed at the general public.

Can the Flesch-Kincaid Grade Level be negative?

Yes. Short sentences built from one-syllable words, like many picture books, push the formula below zero. Treat any negative score as kindergarten level or easier.

Is Flesch-Kincaid the same as Lexile?

No. Lexile is a proprietary measure that uses word frequency against a large reference corpus, and it’s reported on its own scale (for example 500L). Flesch-Kincaid uses only sentence and word length and reports a school grade.

How do I lower my Flesch-Kincaid Grade Level?

Split long sentences in two and choose shorter everyday words. Cutting average sentence length from 20 words to 14 lowers the grade by more than two levels on its own.

Does Microsoft Word use the same formula?

Yes, Word uses the standard Flesch-Kincaid formula. Scores can still differ slightly because Word counts syllables and sentences its own way.

What grade level should a children’s book be?

For a book a child reads alone, at or slightly below their school grade. For a read-aloud, a grade or two higher is fine, because children understand more words than they can read.