calcs.homes
calcs.homes
Enter your building footprint, roof pitch, and eave overhang to estimate total roof surface area — this roof area calculator multiplies the plan area by the slope factor and converts the result to roofing squares.
Estimate only — dormers, hips, valleys, and cross-gables add area this footprint method does not capture.
We add the overhang to each side of the footprint, multiply length by width for the covered plan area, then multiply by the slope factor — √(1 + (pitch÷12)²) — to account for the slope. A roofing square is 100 square feet, so dividing by 100 gives the squares a supplier quotes from.
This gable-style estimate is close for simple rectangular roofs, and hip roofs cover a similar area. Dormers, cross gables, and steep valleys all add surface a footprint cannot show, so add 5–15% for a cut-up roof before ordering material.
A roofing square is 100 square feet of roof surface. Shingles, underlayment, and labor are all quoted per square, so a 2,000 sq ft roof is 20 squares.
Yes — the overhang you enter is added to all four sides of the footprint before the area is calculated, since the roof extends past the walls.
For a plain gable or hip roof it is usually within a few percent. Add 10% or more for roofs with multiple ridges, dormers, or valleys.