Roof Square Footage Calculator
Footprint times pitch factor: the real surface of your roof in square feet and roofing squares.
Roof Square Footage
Enter the footprint and the pitch. Every rate below is editable.
The roof as seen from above, overhangs included. Outline it on a satellite map in LandLens to get this number.
Use the main roof pitch. For roof sections with different pitches, calculate each section on its own.
Roof area
Roof pitch factor table
Multiply the footprint by the pitch factor. Last column: roof surface for a 1,000 sq ft footprint.
| Pitch | Angle | Pitch factor | Roof surface |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | 1,014 sq ft |
| 3/12 | 14.0° | 1.031 | 1,031 sq ft |
| 4/12 | 18.4° | 1.054 | 1,054 sq ft |
| 5/12 | 22.6° | 1.083 | 1,083 sq ft |
| 6/12 | 26.6° | 1.118 | 1,118 sq ft |
| 7/12 | 30.3° | 1.158 | 1,158 sq ft |
| 8/12 | 33.7° | 1.202 | 1,202 sq ft |
| 9/12 | 36.9° | 1.250 | 1,250 sq ft |
| 10/12 | 39.8° | 1.302 | 1,302 sq ft |
| 12/12 | 45.0° | 1.414 | 1,414 sq ft |
How it's calculated
- Pitch factor = √(1 + (rise ÷ 12)²) for an x/12 pitch, or 1 ÷ cos(angle) for a pitch in degrees. A 6/12 roof has a factor of 1.118.
- Roof surface = footprint × pitch factor. A 2,000 sq ft footprint at 6/12 is 2,236 sq ft of roof.
- 1 roofing square = 100 sq ft of roof surface, so 2,236 sq ft is 22.4 squares.
Rates are typical values you can change, not a manufacturer's spec. Ridge caps, starter strips and flashing are not included.
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About the Roof Square Footage Calculator
A roof is bigger than the floor under it, because it slopes. This calculator gives you the real roof square footage from two numbers: the footprint of the roof seen from above and the roof pitch. It also shows the result in roofing squares and lists the pitch factor for common pitches.
Measure the footprint on a satellite map
The footprint is what you see from above, so a satellite map is a good way to measure it. In LandLens, outline the roof edge on the satellite map and use the area it gives you. Trace the outer edge of the eaves so the overhangs are included.
Why use this calculator
- Exact pitch factor - computed from the pitch, not rounded from a chart
- x/12 or degrees - enter the pitch the way you know it
- Squares included - roof square footage and roofing squares side by side
- US or metric - square feet or square meters
Frequently Asked Questions
How do I calculate roof square footage?
Multiply the footprint of the roof (overhangs included) by the pitch factor. A 2,000 sq ft footprint with a 6/12 pitch is 2,000 × 1.118 = 2,236 sq ft of roof.
What is a roof pitch factor?
It is how much longer the sloped roof is than its flat footprint: √(1 + (rise ÷ 12)²). A 4/12 roof has a factor of 1.054, a 6/12 roof 1.118, an 8/12 roof 1.202 and a 12/12 roof 1.414.
How many square feet is a roofing square?
One roofing square is 100 square feet of roof surface. A 2,236 sq ft roof is 22.4 squares.
Is the roof square footage the same as the house square footage?
No. The living area of a house does not include the overhangs and counts every floor, while the roof covers the footprint once and is larger because of the slope. Measure the roof footprint from above instead.
How do I convert a roof angle to a pitch?
Rise per 12 = 12 × tan(angle). A 26.6° roof is a 6/12 pitch and a 45° roof is 12/12. The calculator accepts both forms.
Measure the footprint from above
Outline any roof or building on a satellite map and get its area in seconds with LandLens.
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