How do I calculate roof size?

For a simple gable roof, start with the building footprint, apply the pitch slope factor, then add waste and extra roof areas such as dormers or porch roofs.

What is a roofing square?

One roofing square is 100 square feet of roof surface. Roofing materials and quotes often use squares instead of raw square feet.

Can I calculate roof size by address?

This guide does not measure a roof from satellite imagery or an address. It helps estimate roof size from measurements, footprint, pitch, and known roof sections.

Roof measurement guide

Roof size calculator guide for roof squares, pitch, and shingle area.

Roof size is not always the same as house footprint. A pitched roof has more surface area than the flat plan view, and roofing estimates usually convert that area into roofing squares before figuring shingles, underlayment, waste, and accessories.

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How to estimate roof size

Measure the building length and width for the main footprint.
Enter the roof pitch as rise per 12 inches of run.
Use the slope factor to convert flat footprint into estimated sloped roof surface.
Add extra areas for dormers, porch roofs, additions, or roof sections outside the main rectangle.
Add waste for hips, valleys, cut-up roof shapes, and product/layout rounding.

Roof square calculator basics

One roofing square equals 100 square feet of roof surface. After estimating sloped roof area, divide by 100 to estimate roofing squares. Shingle bundles, underlayment rolls, ridge cap, starter, and labor are then figured from that roof-area starting point.

1,200 sq ft roof

About 12 roofing squares before waste. At 10% waste, plan around 13.2 squares before product rounding.

1,500 sq ft roof

About 15 roofing squares before waste. Add waste and check bundle coverage before buying shingles.

2,000 sq ft roof

About 20 roofing squares before waste. Accessories and quote scope still need to be checked separately.

Roof size by address vs measured roof size

Some tools estimate roof size by address using aerial measurements. RightSizeTools does not pull satellite measurements or guarantee roof area from an address. The calculator is meant for homeowners who have approximate building dimensions, pitch, and known extra roof sections.

For buying materials or signing a roof contract, verify the roof measurement with field measurements, plans, or a contractor measurement before treating the number as final.

What a roof size estimate does not include

Starter shingles and ridge cap
Ice and water barrier or local code requirements
Flashing, drip edge, vents, pipe boots, skylights, or chimney details
Rotten sheathing replacement
Tear-off, disposal, labor, permits, and warranty terms