Ordering concrete in Canada: metres, yards and the short-load fee
One backyard project, two units of measurement, and one mistake that stops a pour halfway through.
6 min read
Is concrete sold by the yard or the metre in Canada?
Ready-mix concrete is sold by the cubic metre, normally in 0.5 m³ increments with a minimum load. Landscape materials — topsoil, mulch, gravel, sand — are still commonly quoted by the cubic yard at supply yards. A single project routinely needs both figures, and the conversion is not round: one cubic yard is exactly 0.764554857984 cubic metres, or about 76%.
Two units on the same job site
This catches people out because both quotes feel authoritative and neither mentions the other.
Phone a ready-mix plant for a slab and you will be quoted in cubic metres. Walk into a landscape supply yard for the gravel base under that same slab and you will be quoted by the cubic yard.
Order ten of the wrong one and you are out by roughly 2.4 cubic metres — enough to matter on any residential job.
The conversion is exact rather than approximate, because the international yard has been defined as exactly 0.9144 metres since 1959.
Depth is where the arithmetic goes wrong
Length and width are almost always in feet or metres. Depth is almost always in inches or millimetres. Multiplying 20 by 16 by 4 without converting that 4 gives an answer four times too large, and it looks plausible enough to phone in.
Common depths worth memorising: 100 mm for a residential slab or walkway, 150 mm for a driveway, 50 to 75 mm for mulch, and 75 to 100 mm for a gravel base.
For a round pad, note the formula uses the diameter, not the radius. Substituting the radius gives a quarter of the true volume — a common and expensive slip.
Converting depth first, before any multiplication, eliminates most of the errors in this calculation.
Why under-ordering is the expensive mistake
The calculated volume assumes a perfect rectangular void. Real excavations never are. Subgrade settles, forms bow outward under the weight of wet concrete, and a hand-dug trench is deeper in places than the string line suggests.
The standard allowance is 5 to 10% on a prepared and formed base, and up to 15% where concrete is poured against earth-formed footings.
Running short mid-pour is far more expensive than the surplus. A second truck attracts a short-load fee — charged per load, so a small top-up delivery costs disproportionately — and the delay leaves a cold joint across the slab, which is permanent and structurally weak.
The extra half cubic metre is cheap insurance against both.
Rough coverage from one cubic yard
Useful for sanity-checking a quote before you commit.
One cubic yard covers about 7.6 m² of concrete slab at 100 mm deep, or about 5.1 m² of driveway at 150 mm. The same yard covers about 10.2 m² of mulch at 75 mm, or about 15.3 m² of topsoil at 50 mm.
If a supplier's quoted quantity is wildly out from those figures for your area and depth, one of you has made a unit error — and it is worth resolving before the truck is booked.
Our calculator returns cubic yards, cubic metres and cubic feet together for exactly this reason.