Test Your Vocab is a research project to measure vocabulary sizes according to age and education, and particularly to compare native learning rates with foreign language classroom learning rates. It functions by means of a test: the first part with a handful of words to determine the general vocabulary level, and a second part with a larger but narrower selection of words to determine the vocabulary level with greater precision.
My total vocabulary size is estimated to be 17,800 words. That's not bad since English is not my native language. Most adults fall in the range 20,000 - 35,000, with the exact median score being 27,123 words. Test Your Vocab.
(via Today I learned something new)