Flesch-Kincaid Calculator
The exact 1975 grade formula, scored against a target you choose. Raw values preserved, syllable guesses flagged, and the sentences pushing your grade up ranked for fixing.
Analysis runs in your browser and your text is never uploaded. By default the draft lives in this tab only and disappears when you close it. Ticking the box stores it in this browser's local storage on this device; Clear wipes it. Avoid the box on shared computers if the text is sensitive.
Type or paste text to compare it against your target grade.
The bar is capped at 0 and 100 for display. The number above is the raw formula value and can leave that range.
Formulas disagree because they weigh sentence length, syllables and letters differently. That spread is real information, so no synthetic average is shown.
Syllables are an English estimate from a heuristic, not a pronunciation dictionary. Possible passive is a be-verb plus participle pattern with common adjectives filtered out; review each match, it is a pointer and not a verdict.
Sentences to review
Ranked by how much each sentence adds to your scores. Click a sentence to select it in the editor. Dismiss anything you disagree with; dismissals last until you clear or reload.
Nothing flagged yet. Long sentences, complex-word clusters and possible passive constructions will appear here.
From formula output to an actual edit
A worked example: "The quick brown fox jumps over the lazy dog." has 9 words, 1 sentence and 11 syllables, so the grade is 0.39 times 9 plus 11.8 times 1.22 minus 15.59, which is 2.3. The two coefficients tell you where your leverage is: a whole extra syllable per word costs almost 12 grades, while a whole extra word per sentence costs 0.39. In practice sentence length is the lever you can actually move, and the sentences-to-review list on this page ranks exactly which ones to split first.
One caution the original researchers would insist on: the formula was validated on adult Navy training material. On three sentences of marketing copy it still computes, but the sample is far below anything it was validated for, and this calculator marks every formula's confidence for your sample size instead of pretending stability.
Flesch-Kincaid FAQ
What is the Flesch-Kincaid grade level formula?
Grade = 0.39 times (words per sentence) plus 11.8 times (syllables per word) minus 15.59. It converts the same two inputs as Flesch Reading Ease into a US school grade: a result of 8.0 means the text reads at an eighth-grade level. It was developed for the US Navy in 1975 to grade training manuals and is now the default grade formula in most writing software.
What Flesch-Kincaid grade should my writing be?
Whatever your audience needs, which is why this calculator asks for a target instead of assuming one. Plain-language and health writing usually aims for grade 6 or below, general web copy for grade 7 to 9, and specialist B2B or legal material can sit at grade 10 to 12. Set the audience preset above and the result says whether you are within, near or above your own target.
Can the Flesch-Kincaid grade be negative?
Yes. The formula is plain arithmetic, and very short simple sentences produce results below zero: "Go now." scores about minus 3. Tools that clamp the result to zero hide that behavior. This calculator shows the raw value, because knowing the formula bottomed out is more informative than a silent 0.
Flesch-Kincaid grade or Flesch Reading Ease: which should I use?
They are two views of the same two inputs. Reading Ease gives a 0 to 100 comfort score, the grade formula gives a US school grade, and they always move together. Use the grade when you think in audiences and school levels, use Reading Ease when you want the classic score bands. This page computes both, plus four other formulas, from one paste.
More free tools: Readability Checker · Flesch Reading Ease · Reading Level Checker · Word Counter