Flesch-Kincaid Reading Level Calculator
The Flesch-Kincaid readability tests turn three simple counts (words, sentences, and syllables) into two well-known scores: a Grade Level that estimates the U.S. school grade needed to follow the text, and a Reading Ease score where higher means easier. Both formulas were developed under a U.S. Navy contract and are used in federal plain-language guidance, so their constants are fixed and standardized. This calculator applies those exact formulas to the counts you enter. Because syllable and sentence counting is the only source of disagreement between readability tools, supplying the counts yourself makes the result fully deterministic.
Flesch-Kincaid formulas
words per sentence (WPS) = words / sentences
syllables per word (SPW) = syllables / words
Grade Level = 0.39 * WPS + 11.8 * SPW - 15.59
Reading Ease = 206.835 - 1.015 * WPS - 84.6 * SPW
These are the published Flesch-Kincaid constants. Grade Level approximates a U.S. school grade; Reading Ease runs roughly from 0 (very hard) to 100 (very easy).
Interpreting the scores
- Reading Ease 90 to 100: very easy, around fifth grade.
- Reading Ease 60 to 70: plain English, around eighth to ninth grade.
- Reading Ease 30 to 50: difficult, college level.
- Reading Ease below 30: very difficult, graduate level.
- Shorter sentences and shorter words lower the Grade Level and raise the Ease score.
Flesch-Kincaid: frequently asked questions
What is the Flesch-Kincaid Grade Level?
The Flesch-Kincaid Grade Level estimates the U.S. school grade needed to understand a text. The formula is 0.39 times the average words per sentence, plus 11.8 times the average syllables per word, minus 15.59. A result of 8.0 means the text is suited to an eighth grade reading level.
What is the Flesch Reading Ease score?
The Flesch Reading Ease score rates how easy a text is to read on a scale where higher is easier. The formula is 206.835 minus 1.015 times words per sentence minus 84.6 times syllables per word. Scores of 90 to 100 are very easy; 60 to 70 are plain English; below 30 are very difficult.
How do I count syllables, words, and sentences?
Count every word, every sentence (a unit ending in a period, question mark, or exclamation point), and the total syllables across all words. Many word processors report these counts. Enter the totals here and the calculator applies the published formulas exactly.
Are these formulas official?
Yes. The Flesch-Kincaid formulas were developed under a U.S. Navy research contract (Kincaid and colleagues, 1975) and are referenced in U.S. federal plain-language guidance. The constants in the formulas are fixed and standardized, so any correct implementation gives the same result for the same counts.
Why might two tools give slightly different scores?
The formulas are identical, but syllable and sentence counting can differ between tools because natural language is ambiguous (abbreviations, hyphenates, decimals). This calculator removes that variation by letting you supply the exact counts, so the arithmetic is deterministic.
Official sources
- U.S. plain-language guidance: plainlanguage.gov (readability testing).
- Defense Technical Information Center: Kincaid et al. (1975), the originating Navy report.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. The formula constants are fixed and published. See our methodology.