I think propane bottles are measured in pounds, though they sell it by the gallon. I think my 10 pound tank holds a little under 5 gallons.
I started with a 10 pound, then added another.
Water and stove should go a long time on a 10 pound. I run a heater during the winter and it uses much more fuel.
My recommendation, is to try what you have an allow for space to add if needed.