When converting ounces to one tenth of a gallon in Imperial units, there are 16. There are 160 ounces to the Gallon overall, although if you were looking at an American gallon, you would have 128 ounces to the gallon.
The American gallon is currently used in the US, Latin America and a handful of Caribbean countries. The UK gallon is the most widely used and it is preferred in the UK and Canada, among a variety of additional countries.
If you would like to make these conversions quickly and easily, without having to do so manually, you can visit AskNumbers.com, fill out the units you want converted and have it done for you.
Interested in learning more about unit conversions? This video from the Khan Academy will help you get started: