I've recently heard a lot of "5 gallons per frog minimum, 10 gallons per frog is better". I'm guessing it's similar for toads?

Personally, depending on how much of the habitat is taken up by foliage-n-furniture, I'm hoping to buy around 1:15, but will probably have to settle for 1:10, based on cost & availability. (I keep getting mixed up in the planning because our local measurements are metric, and this board and much of the online info is in imperial measurements, ha!)