Roof Pitch Calculator (Pitch, Angle and Roof Area)
Enter pitch and building size to get angle, rafter length and roof area.
Your numbers
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Your results
Roof angle (degrees)
Roof angle (degrees)
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Slope (percent)
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Pitch multiplier
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Rafter length incl. overhang (ft)
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Roof surface area (sq ft)
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Roofing squares to buy (100 sq ft)
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Roof Pitch Calculator (Pitch, Angle and Roof Area) by TheCalcTools
How the Roof Pitch Calculator (Pitch, Angle and Roof Area) works
Pitch is expressed as rise over a 12 inch run, for example 6/12.
The angle is arctan(rise ÷ 12). The pitch multiplier √(1 + (rise ÷ 12)²) converts flat area to sloped area.
Rafter length is the horizontal run times the multiplier. Roof area is two planes.
The formula
Angle = arctan(rise ÷ 12)Multiplier = √(1 + (rise ÷ 12)²)
Worked example
Using the default values shown in the calculator:
| Pitch: rise per 12 in of run | 6 |
|---|---|
| Building span (ft) | 28 |
| Roof length along the ridge (ft) | 40 |
| Eave overhang each side (ft) | 1 |
| Waste allowance | 10 % |
- A 6/12 pitch is 26.6° and 50.0% slope, with a multiplier of 1.118.
- Half-span 14 ft + 1 ft overhang = 15 ft run gives a rafter of 16.77 ft. Roof area 1,409 sq ft = 15.5 squares with waste.
Result:
| Roof angle (degrees) | 26.6 |
|---|---|
| Slope (percent) | 50.0 |
| Pitch multiplier | 1.118 |
| Rafter length incl. overhang (ft) | 16.77 |
| Roof surface area (sq ft) | 1,409 |
| Roofing squares to buy (100 sq ft) | 15.5 |
Frequently asked questions
What is a 6/12 pitch in degrees?
26.6 degrees, which is a slope of 50%.
What is a roofing square?
A roofing square is 100 square feet of roof surface.
Sources and further reading
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