Roofing Calculator
Enter your building footprint and roof pitch to calculate the actual roof area, number of roofing squares, bundles of shingles, and underlayment needed.
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Roofing squares
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Shingle bundles
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Roof area (ft²)
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Underlayment rolls
One roll of 15# felt underlayment covers approximately 400 ft² (4 squares). Synthetic underlayment rolls vary; check product label.
What Is a Roofing Square?
A roofing square equals 100 square feet of roof surface. It is the standard unit contractors and suppliers use to price roofing materials. One square typically requires:
- 3 bundles of standard 3-tab or architectural asphalt shingles
- 4 bundles of luxury or premium shingles
- 1 roll of 15# felt underlayment (covers approximately 4 squares)
Roof Pitch Multiplier Table
| Pitch (rise:12) | Slope angle | Pitch multiplier |
|---|---|---|
| 3:12 | 14° | 1.031 |
| 4:12 | 18° | 1.054 |
| 6:12 | 27° | 1.118 |
| 8:12 | 34° | 1.202 |
| 10:12 | 40° | 1.302 |
| 12:12 | 45° | 1.414 |
The actual roof area equals the footprint area multiplied by the pitch multiplier. A 6:12 pitch roof is 11.8% larger than the footprint; a 12:12 pitch is 41.4% larger.
Gable vs. Hip Roofs
- Gable roof — two sloped planes meeting at a ridge; simple and common; lower waste factor
- Hip roof — all four sides slope down to the walls; more wind-resistant; more cuts = more waste
- Mansard / gambrel — more complex; use a higher waste factor (20%+) and consider getting a contractor measurement
Shingle Types Comparison
| Type | Lifespan | Notes |
|---|---|---|
| 3-tab asphalt | 15–20 years | Lightest; least expensive |
| Architectural (dimensional) | 25–30 years | Most common choice today; thicker |
| Impact-resistant | 30+ years | Class 4 rated; may qualify for insurance discount |
| Metal (standing seam) | 40–70 years | Different installation — see a contractor |
| Tile / slate | 50–100 years | Heavy; requires reinforced structure |
Frequently Asked Questions
How do I measure roof pitch? Use a level and a tape measure. Hold a 12-inch level horizontal against the roof surface and measure the vertical rise from the end of the level up to the underside of the roof deck. A rise of 6 inches over a 12-inch run = 6:12 pitch. You can also use a pitch gauge or smartphone app.
How many squares of shingles do I need for a 2,000 sq ft house? A 2,000 sq ft house might have a footprint of roughly 1,000–1,200 sq ft depending on overhangs and shape. With a 6:12 pitch and 10% waste, the roof area would be approximately 1,230–1,450 ft², or roughly 13–15 roofing squares. Use this calculator with your actual dimensions for an accurate estimate.
Should I include the overhangs? Yes. Measure to the drip edge (edge of the shingles), not the exterior wall line. Overhangs are typically 12–24 inches on each side.
