The test you described is useful for determining how many words in a text you will know - i.e. what percentage in a given set of English. That's probably a more

The test you described is useful for determining how many words in a text you will know - i.e. what percentage in a given set of English. That's probably a more useful number, but it's not what parent asked: "I was hoping for [...] how many English worsd [sic] I know." > Obviously both tests become more accurate as the number of words increases but the vocabulary.ugent.be test requires you to test all 60k words to get an accurate result. They could never get an accurate result for words known in a body wih this test - it needs a separate dataset of word frequency. That's not what they're testing.