Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate Flesch Reading Ease and Flesch-Kincaid Grade Level for any text.
This tool scores how easy your text is to read using the Flesch Reading Ease formula (Flesch, 1948) and the derived Flesch-Kincaid Grade Level (Kincaid et al., 1975) -- the two most widely cited English readability metrics, used everywhere from Microsoft Word to SEO content tools.
Paste your text in. Both scores update instantly as you type.
Flesch Reading Ease = 206.835 - 1.015 × (words/sentences) - 84.6 × (syllables/words)
Flesch-Kincaid Grade Level = 0.39 × (words/sentences) + 11.8 × (syllables/words) - 15.59
Higher Reading Ease scores mean easier text (90-100 = very easy, below 30 = very difficult). Grade Level roughly maps to a US school grade.
Syllable counts use a standard heuristic (there's no exact algorithmic rule for English syllables short of a full pronouncing dictionary) -- results are a close estimate, the same approach every readability tool uses.
Imagine a passage of 100 words split into 5 sentences, containing 150 syllables in total. That is 20 words per sentence and 1.5 syllables per word. Plugging into the formulas:
Reading Ease = 206.835 - 1.015 × 20 - 84.6 × 1.5 = 59.6 | Grade Level = 0.39 × 20 + 11.8 × 1.5 - 15.59 = 9.9
The tool would label that text "Fairly difficult" for Reading Ease (the 50 to 59 band) and show a grade level near 10. If you cut the average sentence length to 14 words without changing the vocabulary, Reading Ease rises to about 65.7 and the label moves to Standard. That illustrates the most useful thing about these metrics: they respond quickly to sentence length, which is the easiest lever for most writers to control.
The numbers depend entirely on how words and sentences are counted, so it helps to know the rules used here. Words are runs of letters, digits and apostrophes, lowercased, so "don't" is one word but a hyphenated term such as "well-known" counts as two. Sentences end at a period, exclamation mark or question mark that is followed by whitespace or the end of the text. A decimal like 3.5 does not end a sentence because no space follows the period, but an abbreviation such as "Dr. Smith" does, which shortens the average sentence slightly.
Two consequences are worth remembering. First, headings and bullet points that lack end punctuation get merged into the next sentence, inflating the words-per-sentence figure and lowering your score. Add a period to list items, or paste only running paragraphs, for a fairer reading. Second, numbers such as 2026 count as words but contribute zero syllables, which nudges the syllables-per-word ratio down. Text full of figures, dates or codes may therefore look easier than it feels to read.
The tool converts Reading Ease into a plain label: 90 and above is very easy, 70 to 89 easy, 60 to 69 standard, 50 to 59 fairly difficult, 30 to 49 difficult, and below 30 very difficult. Very short or very simple texts can score above 100, and the grade level can even go negative, because the formulas are not capped. A single short sentence such as "The cat sat on the mat." produces a Reading Ease around 116 and a negative grade level. That is not a bug; it just means the sample is too small and too simple for the scale to be meaningful.
Treat the score as a diagnostic, not a target to chase. Run your draft, find the paragraphs with the longest sentences, and read them aloud. If a sentence needs two breaths, split it. Replace a long word only when a simpler one means the same thing, not merely to raise the number. Compare versions of the same piece over time rather than comparing your article with someone else's on a different subject, since topic and audience change what a good score looks like. Readability is only one part of quality: accuracy, structure and usefulness matter more than any formula.
A Flesch Reading Ease of 60-70 (roughly 8th-9th grade) is a common target for general web content -- accessible without being oversimplified.
Shorten sentences, use simpler words, and break up long paragraphs -- see the Average Sentence Length Calculator for one specific lever.
A heading without ending punctuation is merged with the sentence that follows it, which makes that sentence look longer. Add a period after headings, or paste only body paragraphs, to avoid the distortion.
Yes. The formula has no built-in limits, so extremely simple text can exceed 100 and very dense text can dip below zero. Those extremes usually mean the sample is unusually short or unusual in structure.
They use the same two ingredients, words per sentence and syllables per word, but weight them differently. Reading Ease runs higher-is-easier, while Grade Level approximates the US school year needed to understand the text, so lower is easier.
They can. Digits count as words with zero syllables, and abbreviations followed by a period may be treated as sentence ends. Heavy use of either can shift the scores a few points.
Reference: Google Search Central