To find out how many rolls you need to know the surface area of whatever you’re wrapping. Let’s assume it’s a large box with dimensions height=H, length=L and width=W. All these measurements must be in inches. The surface area is 2(LH+LW+HW) square inches. The size of a roll of wrapping paper is 30 by 72=2160 square in. So divide the surface area of the box by 2160 to give you the number of rolls. If the surface area is less than 2160 sq in then of course one roll will be enough.
If after division you get a number between two integers, for example, 2.4, then you would require 3 rolls. Always pick the higher integer.
EXAMPLE
If the box was a perfect cube with sides 24 inches (2 feet) long, its surface area would be 3456 square inches and you get 3456/2160=1.6 rolls, which means you actually need 2 rolls.