Roof Pitch Calculator

How to measure and use roof pitch

1. Measure vertical rise over a 12-inch horizontal run (or any run you can access safely). A level and tape or a digital angle finder both work.
2. Enter the rise and run. The tool normalizes to /12, then outputs degrees and percent grade automatically.
3. Use the pitch to choose roofing materials: shingles often require ≥2/12–4/12 minimums; metal panels and membranes vary by manufacturer.
4. For framing or rafters, pair the pitch with span tables and local code. This tool is for quick conversions, not structural design.

Safety first: measure from the attic when possible, or use binoculars + gable dimensions to avoid climbing steep roofs.

Slope cheat sheet

Roof pitch basics: measuring, materials, and safety

Pitch (rise per run) drives drainage, material choice, and how you safely work on a roof. A clear understanding reduces callbacks, prevents leaks, and keeps you off dangerous slopes without the right gear. Use this primer to pair the calculator’s numbers with field decisions.

How to measure pitch safely

The classic method is a 12-inch level (or speed square) and a tape measure: level the body on a rafter or shingle, then measure vertical rise at the 12-inch mark to get X/12. If you can’t climb, measure gable height and span from the ground, or use an angle finder from a ladder set safely. Attic measurements are often safer—place the level on the rafter bottom chord and measure rise at 12 inches along the level.

Converting pitch to degrees and percent

Pitch is a ratio; degrees and percent make slope intuitive for trades that don’t use /12. Degrees = arctan(rise/run). Percent grade = (rise/run) × 100. This tool converts automatically—handy when coordinating with manufacturers that publish minimums in degrees or percent instead of /12.

Material minimums and underlayments

• Asphalt shingles: Many brands allow down to 2/12 with special underlayment; 4/12+ is standard. Below the minimum voids warranties and invites leaks.
• Metal roofing: Standing seam with mechanically seamed panels can go lower slope than exposed fastener panels; check the profile’s rating.
• Membranes: TPO/EPDM/PVC are common for “flat” roofs. Even those need slope (e.g., 1/4 in per ft) to avoid ponding.

Snow, wind, and regional considerations

Cold climates often favor steeper slopes (8/12+) to shed snow and reduce ice dams. High-wind zones may limit overhangs, require additional fasteners, or specify lower profiles to reduce uplift. Always pair pitch with local code requirements and manufacturer fastening schedules.

Working on different pitches

Walkable roofs generally cap around 6/12 with proper footwear and care. Above that, use roof jacks, harnesses, and staging. On low-slope roofs, the hazard is slipping on wet surfaces; on steep slopes, it’s uncontrolled sliding. Never compromise on fall protection for a quick measurement—measure from the attic or gable when possible.

Estimating materials with pitch

Pitch determines roof area: Area = (plan area) × pitch factor. For example, 6/12 has a factor ≈ 1.118. This affects shingle squares, underlayment rolls, and ice-and-water shield quantities. Waste increases with complexity and slope; steep or cut-up roofs can add 10–20% waste.

Ventilation and condensation

Ventilation requirements often scale with attic volume and roof design. Steeper roofs create more attic space; ensure intake (soffit) and exhaust (ridge) vents balance. Low slope roofs without vent paths may need alternative assemblies (unvented, fully adhered insulation with vapor control).

If your calculated pitch conflicts with material minimums, confirm measurements from a safer vantage and consult manufacturer specs before proceeding.