How to calculate TTR (type/token ratio)?

Sketch Engine does not display the corpus type/token ratio but provides all data necessary for the calculation. They are on the corpus info page  (https://www.sketchengine.eu/guide/corpus-info-page/):

DASHBOARD – CORPUS INFO – LEXICON SIZE – word >>> this displays the number of unique items in the corpus
DASHBOARD – CORPUS INFO – COUNTS – Words >>> this displays the total numbers found in the corpus 

The most common calculation should be done using Words from COUNTS and word from LEXICON SIZES like this: 

word ÷ Words × 100 = TTR

The result may differ from TTR calculated by a different corpus system. This is because each system defines "word" differently. For example, in English, "don't" can be considered to be one or two words. (It is considered two words in Sketch Engine.)

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