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About this tool
Analyze the complexity of vocabulary in text
The Vocabulary Complexity Analyzer measures how demanding a piece of English writing is by counting words, sentences and syllables and feeding them into four published readability formulas: Flesch Reading Ease (1948), Flesch-Kincaid Grade Level (1975), the Gunning Fog Index (1952) and LIX (1968). It also reports lexical diversity through the type-token ratio and Guiraud's root TTR, and lists the heaviest words in the passage. It is for editors, teachers, technical writers and anyone rewriting a document for a specific reading level.
Open Vocabulary Complexity Analyzer on AltFTool — it loads instantly in your browser.
Paste at least 10 words into the Text to analyse box, or load the Plain guidance, Corporate policy or Narrative sample.
Scores recompute as you type: Flesch Reading Ease with its audience label, then Flesch-Kincaid grade, Gunning Fog index and LIX.
Read the heaviest three-syllable words and the type-token ratio, then press Copy report for the whole breakdown.
Flesch, Flesch-Kincaid, Fog and LIX disagree in useful ways; seeing all four stops you over-fitting to one.
Type-token ratio and root TTR show whether the vocabulary is genuinely varied or just long-winded.
The heaviest three-syllable-plus words are listed, so you know exactly what to rewrite.
60 to 70 for general audiences — that is plain English at roughly an 8th to 9th grade level. Above 90 reads as very easy, 30 to 50 is difficult and usually means college-level readers, and below 30 is very hard going. Most newspapers sit around 60 to 65; insurance and legal documents commonly land in the 20s.
206.835 minus 1.015 times the average words per sentence, minus 84.6 times the average syllables per word. That is Rudolf Flesch's 1948 formula unchanged. Because only two things move the score — sentence length and word length — the fastest way to raise it is to split long sentences and swap multi-syllable words for shorter ones.
For the Gunning Fog Index, a word of three or more syllables — excluding forms that only reach three because of an -es, -ed or -ing ending. LIX uses a different rule, counting any word longer than six letters. Both counts are shown separately here because they flag different words.
It is unique words divided by total words, so 0.8 means four in five words appear only once in the passage. It drops naturally as text gets longer, which makes raw TTR unusable for comparing documents of different lengths — that is why the root TTR (unique words divided by the square root of total words) is shown alongside it.