About Roofing Calculator
Calculate roofing materials by entering roof dimensions and pitch. Get shingle bundles, squares, underlayment rolls, and cost estimates for asphalt, metal, or tile roofs.
How to use
- Enter your roof footprint dimensions: length and width measured from the ground or from a scaled blueprint. You do not need to get on the roof — measure the exterior walls and add the overhang distance (typically 12-18 inches on each side) to get the footprint dimensions.
- Select the roof pitch (slope) expressed as rise over a 12-inch run. Common residential pitches: 4/12 (low slope), 6/12 (standard), 8/12 (steep), and 12/12 (45 degrees). If you do not know your pitch, measure 12 inches horizontally along a rafter or truss in the attic and measure the vertical rise at that point.
- Choose your roofing material: asphalt shingles (most common, 15-30 year lifespan), architectural shingles (dimensional, 30-50 years), metal roofing (40-70 years), cedar shakes (20-40 years), or tile/slate (50-100+ years). Each material has different coverage per unit and waste factors.
- View the calculated roof area in square feet and in roofing squares (1 square = 100 sq ft). The calculator applies the pitch multiplier to convert footprint area to actual roof surface area. A roof with a 6/12 pitch has approximately 12% more surface area than a flat roof of the same footprint.
- Review the materials list: shingle bundles (3 bundles per square for standard 3-tab, 3-5 for architectural), underlayment rolls, drip edge, ridge cap shingles, roofing nails, and ice and water shield (required at eaves and valleys in Canadian climates).
- Estimate total project cost. In Canada, asphalt shingle roofing installed professionally costs $4-$7 per square foot ($400-$700 per square). Metal roofing costs $8-$15 per square foot. A typical 1,500 sq ft roof (15 squares) costs $6,000-$10,500 for asphalt shingles installed.
Frequently asked questions
How many bundles of shingles do I need?
Standard 3-tab asphalt shingles: 3 bundles per roofing square (100 sq ft of coverage). Architectural/dimensional shingles: 3-5 bundles per square depending on the brand and style. For a 1,500 sq ft roof (15 squares) with standard shingles: 45 bundles plus 10-15% waste = 50-52 bundles. Add extra for hip and ridge caps (approximately 1 bundle per 33 linear feet of ridge/hip). Each bundle weighs 60-80 lbs, so plan your lifting and staging accordingly. Most suppliers deliver pallets directly to the roof via boom truck.
How do I calculate roof area from ground measurements?
Measure the building footprint (exterior walls including overhang) and multiply by the pitch factor. Pitch factors: 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. Example: a 30 x 50 foot building with 6/12 pitch = 1,500 sq ft footprint x 1.118 = 1,677 sq ft of roof area = 16.8 squares. For complex roofs with dormers, valleys, or multiple pitches, calculate each section separately and sum them.
What does roof pitch mean?
Roof pitch is the slope expressed as vertical rise over a horizontal distance of 12 inches. A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. Low pitch (2/12-4/12) sheds water slowly and may require special waterproofing but allows easier walking access. Standard pitch (5/12-8/12) balances drainage, attic space, and walkability. Steep pitch (9/12-12/12) sheds snow well (important in Canadian climates), creates more attic space, but requires safety equipment for installation and maintenance. Pitch affects material costs because steeper roofs have more surface area and require more labour.
How much does a new roof cost?
Average costs in Canada per square foot (installed): 3-tab asphalt shingles $3.50-$5.50, architectural asphalt shingles $4.50-$7.00, metal standing seam $9-$16, metal panels $7-$12, cedar shakes $8-$14, concrete tile $10-$18. For a typical 1,500 sq ft roof: asphalt shingles $5,250-$10,500, metal roofing $10,500-$24,000. Costs include tear-off of old shingles (1 layer), new underlayment, drip edge, flashing, ice and water shield, and disposal. Additional costs for: structural repairs, multiple layers to remove, steep pitch premium (25-50% more for pitches over 8/12), and chimney or skylight flashing. If you need to replace decking boards or fascia as part of the roofing project, use the
Lumber Calculator to add those material costs to your budget.
What is a roofing square?
A roofing square is a unit of measurement equal to 100 square feet of roof area. Roofing materials, labour rates, and pricing are commonly quoted per square. A 2,000 sq ft roof is 20 squares. When a contractor quotes $450 per square for asphalt shingles, the material and labour cost for that roof is $9,000. Three bundles of standard shingles cover one square. Knowing your roof size in squares makes it easy to compare contractor quotes and calculate material quantities.
How long do asphalt shingles last in Canada?
Standard 3-tab shingles last 15-20 years in Canadian climates. Architectural (dimensional) shingles with warranties of 30-50 years typically last 25-35 years in practice — manufacturer warranties cover manufacturing defects, not weather wear. Canadian climate factors that reduce shingle life: freeze-thaw cycles causing granule loss, ice damming along eaves, high winds lifting shingle tabs, UV exposure in southern-facing exposures, and poor attic ventilation causing heat buildup. Extending shingle life: ensure adequate attic ventilation (1 sq ft of ventilation per 150 sq ft of attic floor), install ice and water shield at eaves, and trim overhanging branches.
Do I need ice and water shield in Canada?
Yes. Building codes across Canada require ice and water shield (a self-adhesive waterproof membrane) at roof eaves, valleys, around penetrations (plumbing vents, chimneys), and at any area prone to ice dam formation. The minimum coverage is typically 36 inches (3 feet) above the interior wall line at the eaves. In regions with heavy snowfall, extending to 6 feet or more above the wall line provides better protection. Ice and water shield prevents water infiltration when ice dams form at the eaves and force melting snow under the shingles — a common cause of interior ceiling water damage in Canadian winters.
Part of ToolFluency’s library of free online tools for Construction. No account needed, no data leaves your device.