Lee has a valid point - it's not a great idea to post a link to an unfamiliar site and suggest/imply that people go there. But - I've just checked, and see that that site is one that has gone viral on social media recently - and is a test that I have done. I got about 29,000, and a couple of what I would consider to be well educated friends got 30,000. I have no idea what an 'average' native speaker would get. Maybe more like 20-25k?

Why do you think that answers to 50 questions can extrapolate to sizing a vocabulary of tens of thousands of words? It told me I knew 30k+ words, but how does it know it isn't more or less, and why does it matter? I looked at this, and it uses multiple choice questions where it is too easy to choose the right answer by elimination. And it has a strange notion of "synonyms" and "antonyms" that don't really probe your deep understanding of words -- you wind up choosing the option that is least unsuitable. I'm pretty sceptical of both the method and the value of this test -- can you tell us what the point is?

Are you asking a question or are you trying to get people to visit your website? This post smacks of spam or solicitation to me. Please clarify the intent of this post.

I'm not a native and got 22000, do you believe that ? Well, i'm seriously doubting about this figure. Unfortunately given the extension of vocabulary range, you would have to answer around 1000 questions for this test to be accurate in term of probabilities. But no one would take such a tedious test. Also for this test to be really accurate, one would have to classify words from very common to very rare, this is a huge task for a single man. Maybe something collaborative, where 100 random words are picked out the dictionnary, and you have to answer if you ignore/seen but forget meaning/know the word would allow on the long term to build a database with scores associated to words. And only then you will be able to estimate one's vocabulary extend with lesser questions, but still more than 100 meticulously picked out from different categories, so that it is a representative sample of english vocabulary. But I haven't seen something that serious on the web so far. I totally agree with James, 50 questions, this is just a big joke !