Roof Square Footage Calculator
Enter the footprint of the house and the roof pitch and get the roof area in square feet and in squares, with the length of each edge, for a gable, hip or shed roof, and shingle bundles at a generic coverage you can see. The working is shown for an example.
Estimates for planning, not professional advice. Read the full notice.
Example: a gable roof
1,341.64 ft²
- Roof area in squares 13.42 squares
- Eave length 80 ft
- Rake length 67 ft 1 in
- Ridge length 40 ft
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Your project
Enter a size to see your total.
Each product is rounded up once for the whole project, so the total can be less than the items bought alone added together. A line counted from a cut layout (sheets, boards or tiles laid out piece by piece) is counted for each item and added.
Shopping list
| Item | Size | Buy |
|---|---|---|
| Shingle bundles at the generic coverage | shingle bundles | 45 |
Save on this device
Saved projects
No saved projects yet.
Worked example: a gable roof
Show the working
- Footprint: length times width 40 ft × 30 ft = 1,200 ft²
- Pitch multiplier for the rise in twelve 6 in twelve = 1.118
- Roof area: footprint times the pitch multiplier 1,200 ft² × 1.118 = 1,341.64 ft²
- Squares: divide by the area of one square 1,341.640786 ft² ÷ 100 ft² = 13.42 squares
- Add the waste allowance, once 1,341.640786 ft² + 10 % waste = 1,475.8 ft²
- Bundles: divide by the coverage of one bundle, then round up once 1,475.804865 ft² ÷ 33.333333 ft² = 45 shingle bundles
Assumptions
The figures behind the example. Sourced figures link to their source below; a default is a starting value to check against your label or supplier.
| Assumption | Value | Details and changes |
|---|---|---|
| Shingle waste allowance (gable or shed roof) | 10% | |
| Default A common allowance, not a sourced figure. Check your label or supplier. | ||
| Shingle waste allowance (hip roof, dormers, valleys) | 15% | |
| Default A common allowance, not a sourced figure. Check your label or supplier. | ||
| Eave and rake overhang | 0 in | |
| Default Measure your own overhang; 0 uses the footprint. Check your label or supplier. | ||
| Bundles in one square (generic preset) | 3 bundles per square | |
| Default A common count for architectural shingles, not a sourced figure. Check your label or supplier. | ||
Feet and inches, like 12' 6"
Edge lengths by roof shape
Roof area and the true length of each kind of edge for the example footprint, by roof shape
| Roof shape | Roof area | Eave | Rake | Ridge | Hip |
|---|---|---|---|---|---|
| Gable roof | 1,341.64 ft² | 80 ft | 67 ft 1 in | 40 ft | 0 in |
| Hip roof | 1,341.64 ft² | 140 ft | 0 in | 10 ft | 90 ft |
| Shed roof | 1,341.64 ft² | 40 ft | 67 ft 1 in | 0 in | 0 in |
Each row is worked out on its own from the example footprint and pitch with no overhang. A line the shape does not have shows zero, and the lengths are the true lengths along the slope.
Questions
How many squares is a roof thirty by forty feet?
A roof is measured in squares of one hundred square feet. Multiply the footprint by the pitch multiplier for the rise in twelve and divide by one hundred; the example shows the working for a footprint of forty by thirty feet at a six in twelve pitch.
Does a hip roof have more area than a gable roof?
Not for the same footprint and the same pitch on every plane: both are the footprint times the pitch multiplier, and the edge table shows the same area for each. The hip roof has more edge to cut, so its waste allowance in the assumptions starts higher.
How does pitch change the area?
The steeper the roof, the larger the multiplier, so the same footprint gives more area. Change the pitch to see the area and the bundles move.