Roof Area Calculator
Find roof surface area and roofing squares either from a simple rectangular footprint or by adding the sloped faces you measured directly.
Calculate
Results
Draft — press Calculate| Net roof area | 1,220.89 sq ft |
|---|---|
| Roofing squares | 12.21 squares |
| Footprint | 1,092 sq ft |
| Slope multiplier | 1.118 |
There are two honest ways to get roof area. The footprint mode takes a rectangular plan, a shape (hip, gable or shed) and a pitch, then multiplies the footprint by the slope multiplier. The measured-plane mode lets you add the actual sloped faces you measured on the roof and sums them directly, because those numbers are already on the slope and must not be multiplied by the pitch again.
Footprint vs. measured planes
A footprint measurement is taken as if looking straight down; it ignores the slope and needs the pitch multiplier to become surface area. A measured-plane figure is the real distance up the roof, so it is used as-is. Confusing the two is a frequent estimating error: never apply the pitch multiplier to a length you already measured along the slope.
Hip vs. gable and the full-run shed
For a hip and a gable with the same eave footprint and the same pitch, the surface area is the same: footprint times the multiplier. Only the face shapes, cap length and cutting waste differ. A shed (mono-pitch) roof is different: its rise uses the full horizontal run across the building, not the half-span used on a symmetric hip or gable, so do not reuse the half-span rise here.
A multi-face worked example
Suppose a roof has two rectangular faces of 30 × 18 ft and two triangular ends with a 24 ft base and 15 ft slant height. In measured-plane mode you add 2 × (30 × 18) + 2 × (0.5 × 24 × 15) = 1,080 + 360 = 1,440 sq ft, which is 14.4 squares. Each face is entered with its own real dimensions and summed once.
Limitations
Summing rectangles does not automatically model an L-shaped or intersecting roof correctly, because valleys and overlaps change where faces meet. Measure the true faces, account for overlaps, and treat different-pitch sections as separate measured planes. For a single regular hip, the hip roof calculator is faster and also returns rafter and cap numbers.
Frequently Asked Questions
Why is my hip area the same as a gable?
Because surface area depends on footprint and pitch, not on whether the ends are hipped or gabled. The shapes and waste differ, but the area is identical at the same footprint and pitch.
Should I multiply measured faces by the pitch?
No. Measured sloped faces are already on the slope. Only footprint (plan) measurements get multiplied by the pitch multiplier.
Can this handle an L-shaped roof?
Only by measuring each true sloped face in measured-plane mode and summing them, while accounting for valleys and overlaps. The footprint mode assumes a simple rectangle.