The Flesch-Kincaid Grade Level turns sentence length and word length into a US school grade: a score of 8 means an average eighth-grader (about 13–14 years old) should follow the text. It is the most requested grade-level test for content, education and government writing.
The same two inputs as Flesch Reading Ease, re-weighted to predict a grade. Every extra syllable per word adds 11.8 grades; every extra 10 words per sentence adds 3.9.
What score to aim for
Grade 7–9 suits most public-facing web content. US federal plain-language guidance and many health-literacy guides recommend grade 8 or below for material meant for the general public.
Limits to keep in mind
There is no upper limit, and very simple text can go below zero. The grade estimates difficulty from surface features only; it cannot tell whether your ideas are clear or your jargon is explained.
Where it comes from
J. Peter Kincaid and colleagues re-derived Flesch’s formula in 1975 for the US Navy, testing technical manuals on enlisted personnel. It became a US military standard and later the grade shown in Microsoft Word.
Source: Kincaid, J. P., Fishburne, R. P., Rogers, R. L., & Chissom, B. S. (1975). Derivation of new readability formulas for Navy enlisted personnel. Research Branch Report 8-75, Naval Technical Training Command.
How we count syllables, sentences and words, and how our numbers compare on test passages, is documented in Readability formulas explained.
Flesch-Kincaid Grade Level: common questions
What does a Flesch-Kincaid grade level of 8 mean?
A typical US eighth-grade student, around 13 to 14 years old, should be able to read and understand the text. It is a common target for content aimed at the general public.
How do I lower my Flesch-Kincaid grade level?
Split long sentences and swap long words for shorter ones. Because each syllable per word weighs 11.8 grades, replacing “utilise” with “use” or “approximately” with “about” moves the score quickly.
Is there a worked example?
The classic one: “The Australian platypus is seemingly a hybrid of a mammal and reptilian creature.” has 13 words and 26 syllables in one sentence, so 0.39 × 13 + 11.8 × 2 − 15.59 = 13.1. This tool returns 13.1 for it.
Why can the grade be negative?
The −15.59 constant means very short sentences of one-syllable words produce values below zero. Read anything under 1 as “easier than first grade.”
Which is better, Flesch-Kincaid or Flesch Reading Ease?
Neither: they measure the same features. Use the grade when your guidelines are written in grades (schools, government, health) and the ease score when you want a 0–100 scale.