Here are some interesting numbers based on my limited knowledge. Please note, these numbers are just estimates:
Vocabulary Count Grade 1 Student = 1,000+ words
Normal Person (Graduate) = 5,000 to 6,000+ words
University Professor = 15,000+ words
Spelling Bee Winners = 30,000+ (as claimed by them)
College Dictionary (Abridged) = 50,000 - 70,000
Total Words in English Language = 250,000+ (Growing)
Dictionary (Un-abridged) with derivatives = 450,000+
Shakespeare used 60,000 words
The above claims must be wrong. While English has hundreds of thousands of words, many are obsolete. Scientific words enter the language faster than obsolete ones die. I know a great many words, but surely not all. My guess: maybe 8,000 or 9,000 tops. Personal judgment keeps me from ever using the 2,000 or 3,000 oddballs. My education includes six years of Classics in prep school, four years at no mean college, a year of law school, and grad school at the US's supposedly top university. A working English vocabulary uses the 2,000 commonest words over and over. Shakespeare is our language's acknowledged master. An exact count of all words from works published using Shakespeare's name, totals 17,300-plus, not 60,000! Some of his as yet undiscovered works might yield a few hundred new ones, but doubtful. An English professor with a word-collecting proclivity might know 11,000 to 14,000 English words--half or more oddball words. Anyone with the basic 2,000 plus 4,000 more in a range of the more everyday specialties can read, hear, write, or speak very broadly. Claims that an accomplished master of English knows 12,000 or even 20,000 words needlessly scare any trying to master English at a higher level. [The imagined professor is an extreme word-collector not a word-user.] Knowing 6,000 words is challenge enough. Your retrievable vocabulary needs not over 6,000 words to make you a master of the English language.