MeasureMaterial

Roofing Calculator

Estimate roof surface area and roofing squares for a simple rectangular roof using footprint dimensions and pitch.

Footprint length of the roof rectangle (not including complex hips).

Footprint width of the roof rectangle.

Rise over run (inches of rise per 12 inches of run).

Extra material for cuts, spillage, and irregular areas.

Optional purchase helper. Confirm how many bundles cover one square for your shingles.

How to use

Enter footprint length and width, choose a pitch (for example 6/12), set waste, then calculate. Adjust bundles per square only if you want a shingle-bundle estimate and know your product coverage.

How the calculation works

Footprint area is multiplied by a pitch factor derived from rise/run geometry, then waste is applied. Squares equal adjusted area ÷ 100.

Formula

footprint_ft² = length_ft × width_ft; pitch_multiplier = √(1 + (rise/run)²); roof_area = footprint × pitch_multiplier; adjusted = roof_area × (1 + waste%/100); squares = adjusted ÷ 100; bundles = ceil(squares × bundles_per_square)

Example calculation

A 40 ft × 30 ft footprint at 6/12 pitch: footprint 1,200 ft² × √(1+(6/12)²) = 1,200 × √1.25 ≈ 1,341.64 ft². With 10% waste ≈ 1,475.80 ft² ≈ 14.76 squares.

Assumptions

  • Geometry

    Simple rectangular footprint × pitch multiplier

    Material: roofing · Key: geometry

    Does not model hips, valleys, dormers, or multi-plane roofs.

    Source: Geometric model (not a material constant)

  • Roofing square (ft² / square)

    100 ft²

    Material: roofing · Key: square_definition

    Industry unit definition for roofing materials.

    Source: Common US roofing industry unit (1 square = 100 ft²)

  • Default bundles per square (bundles / square)

    3 bundles per roofing square

    Material: roofing · Key: bundle_coverage

    A frequent asphalt-shingle planning convention (1 square = 100 ft²). Bundle coverage varies by product — confirm packaging.

    Source: Planning default — confirm with your product label or supplier quote. Not a lab or manufacturer certification.

Practical notes

  • Measure the building footprint carefully; overhangs may need extra length/width.
  • Steeper pitches increase surface area even when the footprint stays the same.
  • Order starter strips, ridge caps, and underlayment using product guidance — they are not included here.

Limitations

  • Not a professional roofing takeoff.
  • Hips, valleys, dormers, complex shapes, and local code can change material needs.
  • Bundle estimates depend on product coverage assumptions you enter.

FAQ

What does 6/12 pitch mean?
The roof rises 6 inches for every 12 inches of horizontal run. Steeper pitches use larger multipliers.
What is a roofing square?
One roofing square equals 100 square feet of roof surface.
Can I use this for a hip roof?
Only as a rough starting point. Hips, valleys, and cut waste usually need a more detailed takeoff.

Related calculators

Results are planning estimates. See the Calculator Disclaimer.