Text Complexity Calculator

Raw word and sentence counts from a text sample feed four established linguistic metrics here, each capturing a different dimension of complexity. Type-Token Ratio is the percentage of your total words that are unique — a text that repeats the same words often has a lower ratio than one with more varied vocabulary. This is sometimes called "lexical density" in casual usage, but the formally published lexical-density metric (Ure, 1971) is actually content words divided by total words, a different calculation that needs a count of function words vs. content words this calculator doesn't collect — so the type-token ratio here is a related but distinct proxy, not that formal metric. Vocabulary Diversity uses Guiraud's index (unique words divided by the square root of total words), a classic type-token measure that corrects for the fact that longer texts naturally accumulate more repeated words even with equally rich vocabulary — dividing by the square root of length, rather than length itself, keeps the index comparable across texts of different sizes better than a raw type-token ratio does.

Average Sentence Length is simply total words divided by total sentences, a standard proxy for syntactic complexity since longer sentences tend to carry more subordinate clauses and embedded structure. Complexity Score combines all of these with average syllables per word into a single 0-100 rating: 30 points each for sentence length and syllable count, and 20 points each for the type-token ratio and Guiraud's index, weighted toward sentence length and syllable count since those two correlate most closely with how difficult a text is to parse and read. To use this calculator, count (or have a word processor count) the total words, unique words, and sentences in your sample, then estimate or measure the average syllables per word — English prose averages roughly 1.5 syllables per word.