There are an estimated 20 Mio. Bitcoins mined. At the current price of about $8,000, there is about $160 Billion worth of Bitcoins in circulation.
However, not all of these Bitcoins are really in circulation. The creator “Satoshi” still holds an estimated amount of 300,000 and 900,000 Bitcoins and these will likely never be used. Additionally, there were many Bitcoins lost in the early days.