Roof Square Footage Calculator
Add each part of your roof, set its pitch, and get the total sloped area in square feet and roofing squares, with waste for ordering materials.
Footprint × pitch = roof area
Satellite tools and floor plans give you the flat footprint. Shingles go on the slope, which is longer. The steeper the roof, the bigger the gap between the two.
Measure every section that has its own roof plane: the main house, an attached garage, a covered porch. Sections with different pitches need their own multiplier, which is why this calculator lets you add them separately.
Pitch factors
| Pitch | Multiply footprint by |
|---|---|
| 2/12 | 1.014 |
| 3/12 | 1.031 |
| 4/12 | 1.054 |
| 5/12 | 1.083 |
| 6/12 | 1.118 |
| 7/12 | 1.158 |
| 8/12 | 1.202 |
| 9/12 | 1.250 |
| 10/12 | 1.302 |
| 12/12 | 1.414 |
Roof square footage questions
How do I calculate the square footage of my roof?
Measure the house's length and width at the outside walls, add the overhang on each side, multiply them, then multiply by the pitch factor (1.118 for a 6/12 roof). Do this for each section and add them up.
How many square feet are in a roofing square?
One roofing square is 100 square feet of roof surface. A 2,300 sq ft roof is 23 squares.
Is roof square footage the same as house square footage?
No. The roof includes overhangs and slopes upward, so it is usually 10% to 50% larger than the footprint. A two-story house has a smaller roof than its living area because the floors stack.
Can I measure my roof from Google Maps?
You can measure the footprint from satellite view with the distance tool, but satellite images are flat. Multiply that footprint by your pitch factor to get the real sloped area.
How much waste should I add?
About 10% for a simple gable roof, 15% for hip roofs and roofs with valleys, and up to 20% for complex roofs with many dormers.