Roofing Square Calculator (Canada)

How to use this calculator

Enter your roof area — most Canadian shingle scopes use square feet, so that’s the calculator’s default. The unit dropdown also accepts m² if you have metric measurements from a builder’s drawing.

If you only know the building footprint, run it through the roof square footage calculator first to apply the slope factor. A 30 ft × 40 ft footprint at a 6/12 pitch becomes 1,341 sq ft of actual roof surface (13.4 squares).

Why squares still rule in Canadian roofing

Despite Canada’s official metric system, residential roofing has stayed firmly in imperial. Reasons:

• Cross-border supply chain — most asphalt shingle manufacturing for Canadian distribution is in North American factories using ASTM D3462 dimensions (12 × 36-inch shingles, three bundles per square).
• Insurance scoping software — Xactimate and Symbility both default to imperial for residential property scopes.
• Labour pricing tradition — CRCA productivity guides and most provincial ICI ASA agreements quote in squares.

The calculator gives you both — square feet for ordering, m² for permit drawings and architectural calculations.

NBC 2020 underlayment rules

National Building Code 2020 (NBC), Section 9.26, has tightened underlayment requirements:

• Ice and water shield at eaves — minimum from edge of eave to a line at least 600 mm (24 in) inside the warm wall, in any zone where average January temperature is below 0°C. In Quebec and northern Ontario (≤ −10°C average), several municipalities require coverage to 900 mm inside the warm wall.
• Standard underlayment — synthetic (Owens Corning ProArmor, GAF Deck-Armor, IKO Stormtite) or 30-lb felt. Synthetic is now industry default; 15-lb felt is no longer recommended for most pitches.
• Valley underlayment — full-width ice & water shield in all valleys, regardless of climate.
• Step flashing and pipe boots — every penetration sealed with self-adhered membrane.

The calculator’s default of 4 squares per underlayment roll matches a typical 1,000 sq ft synthetic roll. Add ice & water shield separately based on your eave length and valley count.

What the calculator returns

For a typical 22-square Canadian residential roof (roughly a 1,800 sq ft footprint at 6/12) at 10% waste with architectural shingles:

• 22 × 3 × 1.10 = 73 bundles of shingles
• 22 × 1.10 / 4 = 6 rolls of synthetic underlayment
• ~210 lin ft × 1.10 = 231 lin ft of drip edge (24 sticks at 10 ft each)
• ~7,750 nails (rounded, 2 boxes of 5,000 ct)

Add separately:

• 2–3 squares of ice & water shield along eaves (3 ft band, 1,000 sq ft per roll)
• Ridge cap — about 0.4 squares per 40 ft of ridge
• Pipe boots — count by penetration
• Bathroom vent jacks — count by vent

Provincial cost variation in 2026

Installed cost per square (material + labour, average architectural shingle):

• British Columbia (Lower Mainland, Vancouver Island): $625–$725 per square
• Alberta (Calgary, Edmonton): $475–$575 per square
• Saskatchewan / Manitoba: $425–$525 per square
• Ontario (GTA): $575–$725 per square (excluding boutique HOAs)
• Ontario (rest): $475–$600 per square
• Quebec (Montreal): $475–$600 per square
• Atlantic Canada (Halifax, Saint John, St. John’s): $475–$575 per square

The HomeStars and Renomii data we’ve referenced shows quotes can vary by 30% across contractors in the same city — the calculator gets you a defensible material baseline before you collect quotes.

Cold-climate ordering quirks

Roofs in Canada face freeze-thaw cycles that drive several material choices:

• Class 4 impact-resistant shingles (IKO Nordic IR, GAF Timberline AS II) — required by some Alberta and BC insurers in hail-prone zones. Cost roughly 25% more than standard architectural; some carriers offer a 10–15% premium discount that recoups the difference in 4–6 years.
• Metal flashing in cold climates — galvanised steel drip edge can rust at cut edges; aluminium drip edge ($1.50–$2.20 per linear foot vs $0.95 for steel) is now standard for higher-end work.
• Ridge ventilation — Cor-A-Vent S-400, Roll-Vent, or RoofVent systems require continuous ridge slot. Calculator doesn’t return vent quantity — measure your ridge separately.
• Snow guards for metal roofs — required by NBC in many municipalities to prevent sliding-snow injury below entries. Budget separately, typically $25–$40 each.

Sources

• National Building Code of Canada (NBC) 2020, Section 9.26 — Roofing
• Canadian Roofing Contractors Association (CRCA) — Practice Standards for Steep-Slope Roofing
• ASTM D3462 — asphalt shingle standard (incorporated into NBC by reference)
• IKO, BP, GAF Canada, and Owens Corning Canada 2026 product catalogues
• HomeStars 2026 cost data and Renomii market analysis for installed pricing
• CASMA (Canadian Asphalt Shingle Manufacturers Association) installation guidelines