Free construction calculator
Roof pitch calculator
Pitch to degrees, measured rise and run to pitch, rafter length with the overhang, and the roof area in squares from the footprint.
Result
| Pitch | 6/12 |
|---|---|
| Angle | 26.57°50% grade |
| Slope factor | 1.118Roof length per foot of level run |
| Rise to the ridge | 6' 0" |
| Rafter length | 14' 6-7/16"Along the slope, overhang included, before the ridge and plumb cuts |
| Roof area | 2,012 ft² |
| Roofing squares | 20.1222.1 with 10% waste · 3 bundles per square for most shingles |
- Hips, valleys and dormers add waste: 15% is common on cut-up roofs.
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How it works
Pitch is the rise in inches for every 12 inches of level run. A 6/12 roof climbs 6" every foot. The angle is atan(pitch ÷ 12).
The slope factor turns a level length into the length along the roof: factor = √(12² + pitch²) ÷ 12. Rafter length is (run + overhang) × factor, before the ridge and plumb cuts.
Roof area is the footprint (the level area under the roof, overhangs included) times the slope factor. One roofing square is 100 ft².
Worked example
A 6/12 roof is 26.57°, a 50% grade, with a slope factor of 1.118.
A 24 ft span has a 12 ft run per side: the ridge sits 6 ft above the wall plate, and the rafter with a 12" overhang is 14' 6-7/16" along the slope.
An 1,800 ft² footprint at 6/12 is about 2,012 ft² of roof: 20.1 squares, about 22.1 with 10% waste.
Questions people ask
How do I measure roof pitch?
Hold a level against the rafter or the roof, mark 12" along it, and measure straight up (or down) to the roof. That rise is the pitch: 5" means 5/12. If you measure over a different run, enter both and the calculator does the math.
What angle is a 6/12 pitch?
26.57°. A 4/12 is 18.43°, 8/12 is 33.69°, 12/12 is 45°.
How many squares is my roof?
Multiply the footprint by the slope factor and divide by 100. A 1,800 ft² footprint at 6/12 is about 20.1 squares before waste.
How much waste for shingles?
About 10% on a simple gable and 15% or more with hips, valleys and dormers. Starter, ridge cap and underlayment are figured separately.
What is the lowest pitch for shingles?
Shingle makers allow down to 2/12 with special underlayment (2/12 to 4/12 calls for a double layer). Under 2/12, use a low-slope roofing system.
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