Roof measurement in square metres: a metric guide for Canadian roofers
A metric guide for Canadian roofers: roof area in m², the pitch factor, lineal metres of eave, hip and ridge, and the eave membrane, worked on one Ontario hip roof.
In Canada, a roof measured in square metres is plan area in m² multiplied by the pitch factor, then lineal metres for every eave, rake, hip, valley and ridge. The arithmetic is the same as in feet; what changes is the paperwork around it, and the conversions that sneak in when a Canadian supplier still sells by the bundle and the square.
This guide works one roof end to end in metres, so you can check every number.
Why Canadian roofers end up measuring in square metres
Plenty of Canadian crews quote in squares and never touch a metre. But metric reaches the job from three directions:
- Plans and specs. Architects' drawings and engineered trusses in Canada are dimensioned in millimetres. Commercial specs and most government tenders ask for m².
- Permits. Montréal's roofing permit form asks for the roof area in m² or ft², so a metric number goes straight onto the form.
- Other trades. Engineers, building envelope consultants and general contractors on Canadian projects from Alberta to the Atlantic provinces hand over metric takeoffs and expect metric back.
If the plan is in millimetres and the quote is in m², converting to feet and back in the middle only adds chances to slip.
Plan area to true area: the pitch factor in metric
A plan or a satellite image shows the roof from straight above. That is plan area. Shingles cover the sloped surface, which is larger. Multiply plan area by the pitch factor to get true area.
The pitch factor is a ratio, so it is identical in metres and feet. Canadian roofers still name pitch as rise over 12 on metric jobs; a 6/12 roof is simply 500 mm of rise per 1,000 mm of run.
| Pitch | Rise per 1,000 mm run | Degrees | Pitch factor |
|---|---|---|---|
| 4/12 | 333 mm | 18.4° | 1.054 |
| 5/12 | 417 mm | 22.6° | 1.083 |
| 6/12 | 500 mm | 26.6° | 1.118 |
| 8/12 | 667 mm | 33.7° | 1.202 |
| 12/12 | 1,000 mm | 45° | 1.414 |
For how to find the pitch in the first place, see how to calculate roof pitch, or run the numbers in the free roof pitch to degrees calculator.
Worked example: a Canadian hip roof in square metres
A bungalow outside Ottawa, Ontario. Hip roof, one pitch all round at 5/12. Measured over the overhangs, the footprint is 14.0 m × 10.0 m.
Area
- Plan area: 14.0 × 10.0 = 140.0 m²
- True area at 5/12: 140.0 × 1.083 = 151.6 m²
- With an example 12% waste for a hip roof: 151.6 × 1.12 = 169.8 m²
Use your own waste factor; 12% is only the example's.
Lineal metres
- Eaves: all four sides, 2 × (14.0 + 10.0) = 48.0 m. That is your starter and drip edge length.
- Ridge: on an equal-pitch hip, length minus width, 14.0 − 10.0 = 4.0 m.
- Hips: each hip runs 7.07 m in plan (5.0 m × 1.414). The rise over a 5.0 m run at 5/12 is 2.08 m, so each hip is √(7.07² + 2.08²) = 7.37 m true length. Four hips: 29.5 m.
- Hip and ridge cap: 29.5 + 4.0 = 33.5 m.
Bundles
IKO's Canadian data sheets list 3.1 m² per bundle for its Dynasty, Cambridge, Royal Estate and Nordic shingles. So 169.8 ÷ 3.1 = 54.8, round up to 55 bundles. Check the wrapper or data sheet for the product you actually order.
The cross-check in squares
One square is 9.290 m². 169.8 ÷ 9.290 = 18.3 squares, and 18.3 × 3 bundles = 54.9, so 55 bundles again. If your metric and square routes disagree by more than a bundle, a conversion went wrong.
Eave protection in metric, under Canadian codes
The National Building Code of Canada (Sentence 9.26.5.1) sets eave protection by distance, and the distances are metric. Per the APCHQ guide, the membrane runs at least 900 mm up the slope from the roof edge and at least 300 mm inside the inner face of the exterior wall, whichever reaches further. Unheated garages, carports and porches, eaves where the roof edge sits more than 900 mm (along the slope) from the inner face of the exterior wall, steep roofs (1 in 1.5 or steeper) and low-degree-day regions can be exempt.
Provinces adopt their own edition: the Ontario Building Code, the BC Building Code, Alberta's adoption, Québec's Code de construction. Check the edition that applies to the job.
On the Ottawa bungalow, take a 600 mm overhang and a 200 mm wall. From the roof edge to 300 mm inside the wall is 600 + 200 + 300 = 1,100 mm in plan, or 1,100 × 1.083 = 1,191 mm along the slope. That beats 900 mm, so it governs. Membrane: 48.0 m × 1.19 m = 57.1 m², before laps, and a little high at the hip corners. The free ice and water shield calculator runs the same check.
Measuring a Canadian roof in metric with RoofStruct
RoofStruct gives you free, unlimited self-serve measuring and PDF reports, no card. You search a Canadian address, trace the roof on satellite imagery or your own drone or phone photo, and get areas and lineal lengths in minutes.
Switch Settings › Localization › Measurement Units to Metric and you see m and m² instead of ft and ft². The setting is per user, so the estimator can work in metric while the crew lead stays in feet, and it carries into exports. Pitch Notation is a separate setting: rise over 12, degrees or percent. The app runs in English and Canadian French; the PDF report itself is in English. More on the measuring tools.
If you are weighing tools more broadly, our guide to roof measurement software for Canadian contractors covers addresses, language and winter imagery.
Where you trip on metric jobs in Canada
Applying the pitch factor twice. Plans show footprints, satellite tracing gives plan area, but some takeoffs are already sloped. Know which one you are holding before you multiply.
Mixing millimetres and metres. A 14,000 mm wall line typed as 14,000 m is obvious. 1,190 typed as 1.9 is not. Convert the plan to metres once, at the start.
Treating a square as 10 m². It is 9.290 m². Rounding it to 10 under-orders by about 7%, which on a 170 m² roof is four bundles short.
Rounding coverage per bundle. 3.1 m² is the figure on the sheet; 3 m² feels close but adds bundles you will return.
Trusting winter imagery. Snow on a Canadian roof hides valleys and vents. Trace what you can see clearly and confirm the rest on site.
FAQ
How do I convert roof squares to square metres?
Multiply squares by 9.290. Twenty squares is 185.8 m². Going the other way, divide m² by 9.290.
Is the pitch factor different in metric?
No. It is a ratio, so 5/12 is 1.083 whether you measure in metres or feet. Canadian roofers keep calling pitch in twelfths on metric plans.
How many square metres does a bundle of shingles cover in Canada?
For IKO's Dynasty, Cambridge, Royal Estate and Nordic, the Canadian data sheets list 3.1 m² per bundle. IKO Armourshake covers 1.86 m² per bundle. Always check the wrapper or data sheet.
What eave protection width does the Canadian code require?
Under NBC 9.26.5.1, at least 900 mm up the slope and at least 300 mm inside the inner face of the exterior wall, with exemptions. Your province's edition may differ, so check it.
Can I get a roof report in square metres?
Yes. Set RoofStruct's Measurement Units to Metric and the report shows m and m². Done-for-you measurement reports also exist if you would rather not trace: see reports.
Sources
Checked Oct 2026: