Calculator · 2026
Roof pitch calculator
How is roof pitch measured?
Roof pitch is the rise in inches for every 12 inches of horizontal run, written as rise/12. A 6/12 roof rises 6 inches per foot: 26.6 degrees, with 1.118 sq ft of roof for every sq ft of footprint.
Roof pitch chart
| Pitch | Angle | Slope % | Roof area multiplier |
|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1.003 |
| 2/12 | 9.46° | 16.7% | 1.014 |
| 3/12 | 14.04° | 25.0% | 1.031 |
| 4/12 | 18.43° | 33.3% | 1.054 |
| 5/12 | 22.62° | 41.7% | 1.083 |
| 6/12 | 26.57° | 50.0% | 1.118 |
| 7/12 | 30.26° | 58.3% | 1.158 |
| 8/12 | 33.69° | 66.7% | 1.202 |
| 9/12 | 36.87° | 75.0% | 1.250 |
| 10/12 | 39.81° | 83.3% | 1.302 |
| 11/12 | 42.51° | 91.7% | 1.357 |
| 12/12 | 45.00° | 100.0% | 1.414 |
| 14/12 | 49.40° | 116.7% | 1.537 |
| 16/12 | 53.13° | 133.3% | 1.667 |
| 18/12 | 56.31° | 150.0% | 1.803 |
The multiplier is the square root of 1 + (rise/12)². Roof area = footprint x multiplier, before overhangs and waste.
How to measure pitch
- From the attic. Hold a level horizontally against the underside of a rafter, mark 12 inches along it, and measure straight up from that mark to the rafter. That measurement is the rise.
- From a ladder at the eave. Do the same on the roof surface with a level and tape. Stay off the roof unless you are trained to work on one.
- From the ground. Measure the angle with a phone inclinometer against the gable edge and enter it in angle mode.
Pitch and roof cost
The roof cost calculator groups pitch into four bands: flat (2/12, multiplier 1.014), low (4/12, 1.054), medium (6/12, 1.118) and steep (10/12, 1.302). A steeper band means more squares for the same footprint. For counts of bundles, rafters and trusses, see the shingle calculator, rafter calculator and truss calculator.
Pitch, angle and area are geometry; the four pitch bands are the ones the Roof Cost Index calculator uses (methodology). Written by the Thomas Town Digital editorial team.
Roof pitch questions
How do I calculate roof pitch?
Measure the vertical rise over a 12-inch horizontal run. A roof that rises 6 inches in 12 inches of run is a 6/12 pitch. If you measure a different run, pitch = 12 x rise / run.
What angle is a 6/12 roof pitch?
A 6/12 pitch is 26.57 degrees. Its roof area is 1.118 times the flat footprint underneath.
What angle is a 4/12 roof pitch?
A 4/12 pitch is 18.43 degrees, with a roof-area multiplier of 1.054.
What is a 12/12 roof pitch?
A 12/12 pitch rises 12 inches for every 12 inches of run: a 45 degree roof. Its surface is 1.414 times the footprint.
How does pitch change roofing cost?
A steeper roof has more surface to cover for the same footprint, so it needs more squares of material and labor. The multiplier column in the chart shows how much more.