Roof square footage calculator
Convert a building footprint into the actual sloped roof surface area and squares.
Roof square footage calculator
Convert a building footprint into the actual sloped roof surface area and squares.
Enter your footprint dimensions to see the roof area.
Roof surface area
Project summary
How it works
This estimates sloped roof area from a rectangular footprint and pitch. Actual area varies with roof style, hips, valleys and overhangs, none of which this calculator models.
Roof square footage calculator
Why footprint and roof area are not the same number
The square footage of a house as measured from the ground, its footprint, is smaller than the actual roof surface unless the roof is completely flat. A sloped roof covers more physical area than the footprint beneath it, and the steeper the pitch, the bigger that difference gets. This calculator applies the pitch to convert one into the other.
For general estimating, not a shingle order
This tool stops at square footage and roofing squares, useful for a rough materials budget, an insurance estimate or a permit application. It deliberately does not go further into bundle counts or waste allowance for a specific shingle package: the roof shingle calculator covers that purchasing step, since bundle coverage varies by product.
Frequently asked questions
How do I convert my house footprint to roof area?
Multiply the footprint area by the pitch multiplier: sqrt(pitch squared + 144) divided by 12. A 1,200 square foot footprint at a 6 in 12 pitch has a roof area of about 1,342 square feet, or roughly 13.4 squares. Enter your own footprint and pitch above for the exact figure.
What is a roofing square?
A roofing square is 100 square feet of actual roof surface area, the standard unit roofing materials are priced and sold by. A 1,342 square foot roof is about 13.4 squares.
How do I calculate my roof square footage?
Multiply the length by the width of each roof section to get the area, then add the areas together. Account for slope by multiplying the flat area by the slope factor. The calculator does this automatically when you enter your building dimensions and roof pitch.
How much larger is the roof than the house footprint?
A typical roof is 10 to 40 percent larger than the building footprint depending on the overhang and slope. A 4 in 12 pitch adds about 6 percent to the area. A 12 in 12 pitch adds about 41 percent. The calculator computes the exact roof area from your dimensions and pitch.
Do roof measurements include overhangs?
Yes, the calculator includes overhangs if you enter the roof edge dimensions rather than the wall dimensions. Most roofs overhang the walls by 12 to 24 inches. Measure from the outer edge of the overhang on each side for the most accurate result.
How many squares is my roof?
Divide your total roof square footage by 100 to get the number of squares. A 2500 square foot roof is 25 squares. Add waste, typically 10 to 15 percent for simple roofs and more for complex shapes. The calculator shows squares and bundles so you can order the right amount.
How do I measure a complex roof?
Break the roof into rectangles and triangles. Measure each section separately, calculate the area, and add them together. Hip and valley roofs have more facets than gable roofs. The calculator handles simple rectangles, and for complex roofs you can calculate each section and sum the results.
Does chimney or skylight area get subtracted?
No, chimney and skylight areas are not subtracted from the roof area. You still need to flash and shingle around them, and the waste from cutting around penetrations is covered by the waste factor. The calculator uses the gross roof area.