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Roof Pitch Calculator

Convert rise and horizontal run into a pitch ratio, angle and slope multiplier.

Your project measurements

in
in

Results update as you type. U.S. units. Defaults are editable planning examples. Use product labels and supplier specifications.

Your material plan

Enter your measurements to see your plan.

A quantity estimate, not a supplier quote. Confirm order increments, delivery and project specifications.

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How this calculation works

Enter measurements above to see the worked calculation.

Rise and run use the same unit

A rise of 6 inches over 12 inches of horizontal run is a 6:12 pitch. The angle is about 26.57 degrees and the surface multiplier is about 1.118. If your rise and run are measured in feet, convert both to inches before entering them.

Horizontal run is not the sloped length

Run measures the horizontal distance beneath the slope. Using the diagonal rafter length as run produces the wrong angle. This calculator converts geometry only; it does not determine whether a roofing product is suitable for that pitch. Consult its installation instructions.

Use actual coverage, not just a bundle count

A roofing square is 100 square feet. Bundle coverage depends on the selected shingle. The example coverage is approximately one-third of a square; use the manufacturer’s listed coverage for your product. Starter strips, ridge caps, underlayment and fasteners are separate products; the roofing calculator estimates starter, ridge cap, underlayment and drip edge from your roof edges.

Keep the geometry simple

The footprint method assumes one consistent pitch over the measured horizontal footprint, including overhangs. Complex roofs with dormers, valleys or mixed pitches need separate measured sections. This tool does not determine roof structure, flashing requirements or safe access.

Product reference: Owens Corning roofing product documents. Confirm the current label for your chosen product.

Make the estimate your own

Measure the actual area, choose your product and update the allowance. Costs use the price you enter. Delivery, tax, labor and preparation are excluded unless this tool has a separate field for them. The result rounds whole packages up; displayed decimal quantities are not supplier order increments.

Before you order

  • Check dimensions and units, including depth and openings.
  • Confirm the selected product’s coverage, yield or density.
  • Ask your supplier about package sizes, minimum orders and delivery access.
  • Keep a copy of your measurements with your material plan.

Method v1.0 · Updated October 12, 2026. Read our methodology.