Corn snake can be housed well in a 32qt tub. A garter, king, and milk snake could probably use the same size, or slightly bigger (40-42qt) depending on the sub species. A hognose could probably be fine in a 28qt, I think.
Rule of thumb is that the snake can stretch it's body out around the perimeter of the cage.
It depends on the age and size of the snake. I have 16 quart Sterilite tubs for hatchlings/neonates and 28 quart Sterilite/Rubbermaids for most adults. The 41 quart Sterilites are larger tubs that can work as well.