square
A unit used in measuring roof area equivalent to 100 square feet (9.29 m²) of roof area. The materials for roofing jobs are often billed by the square in the United States.
square: 100 sq ft of roof, the billing standard
In roofing, a square is a unit of measurement equal to 100 square feet (9.29 square metres). This is the standard lot by which asphalt shingles, slate, tile, metal panels, and other roof coverings are priced and ordered in North America. When a contractor quotes a roofing job, they count the roof area in squares rather than in square feet, then multiply by the material cost per square.
The square originated as a practical working unit because 100 square feet is roughly the amount of material a single roofer can install in one day, making it convenient for scheduling and labor estimation as well. A typical residential roof of 2000 square feet equals 20 squares. Materials are typically packaged to cover one square; for example, asphalt shingle bundles are bundled so that three bundles cover one square when applied with standard overlap.
Calculating squares from a roof plan requires measuring the area of each plane (accounting for pitch, which increases true area beyond the horizontal projection) and dividing by 100. A steep pitch increases the number of squares needed compared to a flat or low-slope roof of the same footprint. Waste factor, typically 10 percent, is added to account for cuts around penetrations, valleys, and edges.
Material pricing per square varies with product type and grade. Standard asphalt architectural shingles might run $25 to $50 per square for materials alone; premium asphalt or metal roofing runs higher. Underlayment, flashing, fasteners, and disposal are often quoted separately or bundled into a total contract price rather than per-square rates. Labor is also quoted per square or as a lump sum for the entire job.
The term "square" is largely confined to the roofing trade in English-speaking regions. It does not apply to siding, flooring, or wall coverings, which use per-square-foot or per-linear-foot pricing. The square has persisted despite metrication because the roofing industry in the United States continues to operate in imperial units, and the term is deeply embedded in supplier catalogs, labor estimates, and trade communication.