At the moment of writing, on October 30, 2017, the Bitcoin supply is 16,654,762 BTC. Note that the maximum supply limit of Bitcoin is 21 million. However, it may happen that these conditions may change after a future hard fork that would leave original Bitcoin behind similar to Ethereum Classic.
But, it is difficult to know how many Bitcoins are in moving at this point. Besides, what do you mean by currently? – this second, minute, day, month?
Today, 377,831 BTC were traded according to CoinMarketCap, which means over 377 thousand Bitcoins have currently been in circulation if “currently” refers to 24 hours.
If you don’t refer to the dynamic meaning of “circulation”, then, as mentioned, 16,654,762 were mined until this day. These coins are available for transactions and can be used by owners at any time. Here is the available BTC supply throughout the years:
Some owners keep huge amounts of Bitcoin and don’t move the most of it within the network. It suggests that their Bitcoins are static, and if considerable volumes of Bitcoin keep this way, a scarcity phenomenon could take place, which can push the price up. This is why we need Bitcoin owners to trade their coins more frequently so that a Bitcoin velocity would be formed.
Today, over 290 thousand transactions have been processed, and the day is not over yet – more than half of it has passed.
The number of transactions is not always directly related with the amount of Bitcoin traded during a certain period because as the BTC price grows, people tend to trade less BTC units per transaction. For example, when BTC was $10, one could easily sell 100BTC per transaction. Today, 100 BTC is already massive, and there are less individuals that could make such transactions. Thus, the number of Bitcoins per transaction tend to go down, as people often trade less than 1 BTC.