How many words do we know? What would it take to identify and count all words known to a person? A hard nut to crack, isn't it? No doubt, one can dig into a thick hardback dictionary to flip page by page and count all familiar words. But do you want to do that, and how long would it take? It would be like trying to count all sand-grains in a handful of sand.
Is there a better way? Yes, there is. Let's first reckon, say 20 grains, weigh them and then, according to their weight, figure out the number of the rest by using a math algorithm. In our case, weight means the frequency of a word only vice versa, thus, the more frequent (or simple) is the word, the less its weight. We've built a counter and “weighing scales” for you, so you don't have to bother with all this weight-math stuff.
Take the Test and Find Out the Number of Words You Know!
If you really want an accurate result, be honest. Do not tick the words that you might have seen or heard once upon a time, and they seem to be familiar (but you have doubts about their meaning). Don't look up words in a dictionary. And don't worry about your time, the test will take only a few minutes to complete. If your vocabulary is big enough, you will have to go through at most 152 words. Take the test and compare your score with other people from around the world.
Check the box for each word whose definition (at least one) you know for sure.
Hint for Windows users: you can navigate through the checkboxes using the Tab key and select with the Space bar. To skip a word hit Tab once again.