One square means 100 square feet
A roofing square is a unit of area: 100 square feet of roof surface. A roof with 2,000 square feet of surface area has 20 roofing squares.
Roofing squares describe coverage. The quantity a contractor orders may be higher to account for cutting, layout, and product packaging.
The footprint and roof surface are different
An outline traced on a straight-down image measures the roof’s horizontal footprint. Follow the outside roof edges, including overhangs. The home’s interior floor area is not the same measurement, and a second story does not double the roof area.
A sloping roof has more surface area than its footprint. A 6:12 pitch rises 6 inches for every 12 inches of horizontal run. For that slope, the roof surface is about 1.118 times the horizontal area: a 2,000-square-foot footprint becomes about 2,236 square feet of roof surface.
Different roof sections can have different pitches. Trace or enter separate, non-overlapping sections and give each one the appropriate pitch.
Keep the waste allowance separate
If a measured roof surface is 2,000 square feet, it has 20 coverage squares. With an illustrative 10% waste allowance, the planning material quantity is 2,200 square feet, or 22 squares.
That percentage is an example, not a recommendation for every roof. Hips, valleys, cuts, product dimensions, and the installation pattern affect the material needed. Your roofer determines the allowance and rounds the order to the product’s package quantities.
What the planner can and cannot measure
The planner calculates area from the shape and pitch you supply. A public aerial image may be older or less detailed than a professional roof report, and trees or shadows can hide edges. Confirm that you are looking at the correct building.
An uploaded image needs a known distance to establish its scale. Use a true overhead image; an angled photograph can distort the area. For entered dimensions, measure the outside roof footprint and include overhangs.
The result is a planning estimate. It does not inspect the roof, diagnose damage, establish a final price, or create a verified material order.