Roof square footage calculator
Type the length, width and pitch of each roof section and this calculator gives the sloped roof area in square feet, the number of squares, squares with waste for the roof shape, and shingle bundles to order. Add a garage or porch roof as its own section. Free, no account.
Roof sections
Measure each section from above, eave to eave, so the overhang is included. Give a lower garage or porch roof its own section when its pitch differs.
- Main roof: 1,344 sq ft × 1.118
- 1,503 sq ft
- Garage: 528 sq ft × 1.054
- 557 sq ft
- 2,059 sq ft ÷ 100
- 20.6 squares
- + 10% waste, × 3 bundles a square, rounded up
- 68 bundles
Worked out in your browser from the numbers you type. Nothing is looked up or saved. No prices are shown here. Confirm every number on site.
How to calculate roof square footage
Roofers price by the square: 100 square feet of roof surface, measured on the slope. Get there from the ground in five steps.
- Measure each roof section's length and width from above, eave to eave. On the ground, that's the wall length plus the overhang on each side.
- Find each section's pitch: the rise in inches over 12 inches of run.
- Multiply each footprint by its pitch multiplier to get the sloped area, then add the sections.
- Divide by 100 for squares.
- Add waste for the roof shape and round up to whole bundles.
ExampleA house with a lower garage roof
- Main roof: 42 × 32 at 6/12 (× 1.118)
- 1,503 sq ft
- Garage: 24 × 22 at 4/12 (× 1.054)
- 557 sq ft
- Sloped roof area
- 2,059 sq ft
- 2,059 ÷ 100
- 20.6 squares
- With 10% waste for a gable roof
- 68 bundles
At 3 bundles a square, 68 bundles is 22.67 squares of shingles. Starter strip and ridge cap are extra.
Squares, waste and bundles
A square is 100 sq ft of roof. Order more than you measure to cover cuts at hips, valleys, rakes and starter courses. Roofs with more sections and angles waste more.
Most asphalt shingles come 3 bundles to a square, and some heavier lines come 4. The calculator rounds the order up to whole bundles. These are Measured Bid's starting waste allowances, and you can change each one.
Starting waste allowance by roof shape
| Roof shape | Waste | Squares to order on our example |
|---|---|---|
| Gable | 10% | 22.7 |
| Hip | 15% | 24.0 |
| Complex (several roof sections) | 17% | 24.3 |
| Shed (single slope) | 8% | 22.3 |
| Low slope | 5% | 21.7 |
Pitch multipliers for common roofs
The steeper the roof, the more surface it has over the same footprint. A 12/12 roof has about 41% more roof than its footprint, and a 4/12 roof about 5% more.
Don't know the pitch? The roof pitch calculator turns a rise and run or an angle into a pitch, and has the full chart from 1/12 to 24/12.
Pitch multiplier and 1,000 sq ft of footprint
| Pitch | Multiplier | Roof area |
|---|---|---|
| 3/12 | 1.031 | 1,031 sq ft |
| 4/12 | 1.054 | 1,054 sq ft |
| 5/12 | 1.083 | 1,083 sq ft |
| 6/12 | 1.118 | 1,118 sq ft |
| 7/12 | 1.158 | 1,158 sq ft |
| 8/12 | 1.202 | 1,202 sq ft |
| 9/12 | 1.250 | 1,250 sq ft |
| 10/12 | 1.302 | 1,302 sq ft |
| 12/12 | 1.414 | 1,414 sq ft |
Skip the tape: measure the roof from an address
Measuring a footprint and guessing the pitch gets you close. Measured Bid's free roof measurement tool reads every roof plane from Google's aerial roof data instead, with its pitch and sloped area, so there's nothing to multiply.
On our model house that's 2,344 sq ft, or 23.4 squares, across 4 planes. Check the roof on site before you order.
Planes
- North, 5/12962 sq ft
- South, 5/12962 sq ft
- East, 5/12210 sq ft
- West, 5/12210 sq ft
Price the roof with your rates
Squares are the quantity. In Measured Bid you add a price per square for each material, tear-off per layer, waste by roof type, a steep-roof adjustment and a job minimum.
FAQ
How do you calculate roof square footage?
Measure the roof's footprint from above, eave to eave, and multiply it by the pitch multiplier. A 42 by 32 ft footprint is 1,344 sq ft. At 6/12 the multiplier is 1.118, so the roof is about 1,503 sq ft. Add each roof section on its own when the pitches differ.
How many squares is my roof?
Divide the sloped roof area by 100. A 1,503 sq ft roof is 15.0 squares. Order more than that to cover cuts and waste.
How much waste should I add?
Measured Bid starts at 10% for a gable roof, 15% for a hip roof and 17% for a complex roof with several sections. Change it to match your crew and the product.
How many bundles of shingles are in a square?
Most asphalt shingles come 3 bundles to a square. Some heavier architectural lines come 4 to a square, so check the wrapper and set bundles per square in the calculator. Starter strip and ridge cap are ordered by the foot, on top of the field shingles.
Can I get roof square footage from an address?
Yes. Measured Bid's free roof measurement tool reads every roof plane from aerial data, with its pitch and sloped area, so there's no footprint or multiplier to type.
Related pages and tools
Price roofs from an address
Add your rates once. Your team gets estimates from an address, and homeowners get a price range on your website. 14 days or 5 estimates free, no card.