Roofing materials are measured in squares, which is essentially 100 square feet of roof regardless of whether the 100 square feet is a 10’ X 10’, a 2’ X 50’, or a 4’ X 25’. The specific shape does not matter as much as pure measurements in order to correctly gauge how many bundles of shingles to buy. Until the late 1970s, shingles were sold by weight. They are now marketed and sold by “year”, meaning how many year warranties they come with such as 20-year, 25-year, and 30-year.
