How to Count the Number of Words You Know in Any Foreign Language

It was in 1994.

I went from Russia to Germany for studying at the Technical University of Chemnitz-Zwickau. It took about 5 days to get there by train. I didn't want to waste that time in the train and decided to calculate my German vocabulary.

But how could I do it? To take a dictionary and count all the familiar words there it would have been too time consuming. Even my 5 day journey wouldn't  have been long enough to look carefully through the whole dictionary. So I found another way.

I took my Russian German dictionary and counted the words I know only on every tenth page of it. Then I multiplied the result by 10 and got the approximate number of words I know in the German language, the approximate one but pretty close to the exact volume of my vocabulary. It was 6,000 words.

After 4 months of studying in Germany I went back to Russia and on my way home I repeated the same action with my Russian German dictionary. I counted the words on every tenth page but began doing it from a different page than I had done it before. By that time I had already known 12,000 German words.

Maybe you know some other ways of calculating your vocabulary? Feel free to criticize my method and to suggest your own one.