It depends. The simple answer is quite a bit. The not so simple answer (i.e. the more specific one) depends on the shape of the vessel and the net tonnage of the vessel (i.e. the volume of the ship not used for machinery, crew accommodation, operation equipment, etc, or more simply the volume of the cargo holds) I don’t know off the top off the top of my head, but actually thinking about it 10,000 dwt is a small sized tanker, relatively speaking. I mean, the RMS Titanic’s dwt was a little over 13,000 tons, and most tankers today are a fair bit larger than she was, pushing upwards of 200 feet longer and much wider than she was. Sorry I couldn’t answer your question more specifically. I know that supertankers (over 100,000 dwt ish) can carry multi millions of barrels, if that helps.