What is roof pitch?
Roof pitch describes how steep a roof is. In the US it’s written as rise over run, with run fixed at 12 inches: a 6/12 roof rises 6 inches for every 12 inches it extends horizontally. The same steepness can be expressed as an angle (6/12 ≈ 26.6°) or a percentage slope (50%).
How to measure your roof pitch
- From the attic or on the roof, hold a level horizontally against a rafter or the roof surface.
- Measure 12 inches along the level from where it touches the roof.
- Measure straight up (or down) from that 12-inch mark to the roof — that number is the rise.
Phone apps with a level can also measure the angle; enter the matching rise using the chart.
Estimating roofing materials
A sloped roof has more surface area than the floor plan below it. The pitch multiplier (√(1 + (rise/12)²)) converts the footprint into true roof area. Roofers sell materials by the square — 100 square feet of roof. Most asphalt shingles come in 3 bundles per square. Add 10–15% for waste, cuts, hips, ridges and starter rows (more for complex roofs with many valleys).
| Pitch | Typical use |
|---|---|
| Under 2/12 | Flat roofs — membrane roofing (TPO, EPDM), not shingles |
| 2/12–4/12 | Low slope — shingles possible with extra underlayment |
| 4/12–9/12 | Most common residential roofs; walkable up to about 7/12 |
| 9/12 and up | Steep roofs — need roof jacks and harnesses; more labor |
Notes
This calculator assumes a simple gable roof with the same pitch on both sides. Hip roofs, dormers and multiple sections need each plane measured separately. Always confirm quantities with your supplier or roofer. For floor or lot areas, use the square footage calculator.
Frequently asked questions
What angle is a 4/12 roof pitch?
About 18.4 degrees.
What is the most common roof pitch?
Between 4/12 and 9/12 for houses in the US, with 6/12 very common.
How many bundles of shingles are in a square?
Usually three bundles cover one square (100 square feet).
What is the minimum pitch for shingles?
Generally 2/12 with special underlayment; 4/12 or steeper is standard.