A roof pitch calculator determines the steepness of a roof, expressed as a ratio. This is crucial for architects, builders, and homeowners planning construction or solar installations.
Planning calculator only. Do not rely on this page alone for structural design, permitting, code compliance, engineering signoff, procurement quantities, or contractual commitments.
Roof pitch represents the slope of a roof as a ratio of rise over run, usually measured in inches per foot or meters per meter.
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The vertical rise of the roof
The horizontal run of the roof
| rise | run | pitch | angle |
|---|---|---|---|
| 1 | 12 | 1/12 | 4.76° |
| 2 | 12 | 2/12 | 9.46° |
| 3 | 12 | 3/12 | 14.04° |
| 4 | 12 | 4/12 | 18.43° |
| 6 | 12 | 6/12 | 26.57° |
| 8 | 12 | 8/12 | 33.69° |
| 10 | 12 | 10/12 | 39.81° |
| 12 | 12 | 12/12 | 45° |
Pitch = Rise / RunThe pitch ratio is simply the vertical rise divided by the horizontal run. To get the angle: Angle = arctan(Rise / Run) × (180 / π). The roofing ratio normalizes run to 12 (e. g. , 6/12 means 6 ft rise per 12 ft run).
Slope percentage = (Rise / Run) × 100
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Most residential roofs fall between 4/12 and 9/12 (18°–37°). Below 3/12 is considered low-slope and requires special waterproofing materials. Above 12/12 (45°) is very steep and may need extra safety measures during installation.
Steeper pitches (higher rise/run) require more shingles, underlayment and labor because of increased surface area and safety requirements. A 12/12 roof can use up to 40–50% more materials than a 4/12 roof.