Roofing Calculator

Estimate roof area, roofing squares, underlayment, nails, starter strips, ridge caps, valley material, and hip material. The calculator supports multiple roof sections, roof styles, roofing materials, feet or meters, and pitch multipliers.

How to use this calculator

Choose roof style, material, and measurement unit. Add one or more sections with length, width, roof pitch, valleys, and hips. The primary result is total roof area, followed by squares needed, waste factor, additional materials, and a section breakdown.

Formula

Each section starts with footprint area and applies the selected pitch multiplier:

$section\ area = length \times width \times pitch\ multiplier + valley\ area + hip\ area$

For one 30 ft by 20 ft section at 4/12 pitch, base area is 600 sq ft and pitch-adjusted area is 636 sq ft. Asphalt shingles add 15 percent waste, so material area is about 731 sq ft, or 8 roofing squares.

Roofing takeoff tips

A roofing square is 100 sq ft of material. Underlayment rolls are estimated from roof area before waste, while nails depend on squares and material. For pitch conversion, use the roof pitch calculator. For flat deck or room footprints, use the square footage calculator.