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Concrete calculator

Last updated: By ConcreteFinder Research Team

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Concrete is sold by volume, so every quantity question is the same question: length times width times depth, converted into the unit your supplier quotes in. Canadian ready-mix trucks bill in cubic metres, most homeowners measure in feet, and bags are labelled in cubic feet, which is why the answer below is given three ways at once. Pick the shape you are pouring, enter the dimensions, and the volume, the bag count and the delivered cost all move together.

How much concrete do you need?

Order volume, including 10 percent waste

5.43 cubic yards / 4.15 m³

Measured volume, before waste
133.33 cu ft
Same volume in cubic yards and cubic metres
4.94 yd³ / 3.78 m³
30 kg bags (each yields 0.50 to 0.52 cu ft)
283 to 294 bags
Bagged material at $6.20 to $7.58 a bag
$1,755 to $2,229
Ready-mix delivered, $175 to $350 per m³ across three Ontario sources
$727 to $1,454
Partial-load charge, because this pour is under 5 m³
$300 to $400

Under about 5 cubic metres a truck charges a partial-load fee on top of the rate, so the cost per cubic metre climbs. Builders Ontario puts the point where ready-mix overtakes bags at roughly 0.75 to 1 cubic metre.

Volumes are geometry, not an estimate. Material prices are the published ranges named on this page and exclude 13 percent HST, delivery beyond a supplier's free radius, pump hire and the winter surcharge. Labour, forming, base prep and finishing are not in these figures.

How the volume is worked out

Nothing here is modelled. Each shape is plain geometry, written out so you can check the answer on paper:

  • Slab, pad, driveway or patio. Cubic feet = length in feet times width in feet times thickness in inches divided by 12.
  • Strip footing. Cubic feet = total length in feet times width in inches divided by 12 times depth in inches divided by 12.
  • Round column or sonotube. Cubic feet = pi times the radius in feet squared times the height in feet, times how many. The radius in feet is the diameter in inches divided by 24.
  • Steps. A flight is treated as stacked rectangular blocks: the top step is one riser deep, the next is two, and so on, so the total is width times run times rise times n(n+1)/2, plus a landing block one riser thick.

Converting is arithmetic: divide cubic feet by 27 for cubic yards, or multiply by 0.028316846592 for cubic metres, because a foot is exactly 0.3048 of a metre.

What the calculator cannot know

Volume is the easy half. The parts that move a real invoice sit outside the geometry. A slab poured on soft fill needs more excavation and more granular base than one on undisturbed ground, and both change the depth you actually pour to. Over a footing trench dug by machine, the sides slump, which is why ConcreteFinder sets the waste allowance higher for footings than for a formed slab.

Access changes the price rather than the quantity. If a truck cannot back to the forms, the concrete goes through a pump, and 2AZ Group puts a GTA line pump at $800 to $1,200 and a boom pump at $1,200 to $1,800 for the visit. Timing matters too: Canada Building Materials adds $22.00 per cubic metre from November 1 to April 30, and 2AZ Group puts winter surcharges at $20 to $40 per cubic metre from November through March.

Finally, none of the material figures on this page include labour, forming, reinforcement, base preparation, finishing or 13 percent HST. For an installed price per square foot, the Toronto concrete cost guide prices the whole job rather than the mix.

Frequently asked questions

How do I calculate how much concrete I need?

Multiply the three dimensions in the same units. A slab is length in feet times width in feet times thickness in inches divided by 12, which gives cubic feet. Divide by 27 for cubic yards, or multiply by 0.0283 for cubic metres. A 20 by 20 foot pad at 4 inches is 133.33 cubic feet, 4.94 cubic yards or 3.78 cubic metres.

How many bags of concrete make a cubic yard?

Basalite states that 66 of its 25 kg sacks fill a cubic yard and 86 fill a cubic metre. Working from the 30 kg bag instead, Sakrete Canada gives a yield of 0.014 cubic metres, half a cubic foot, so a cubic yard takes about 52 to 54 of them.

How much extra concrete should I order?

Builders Ontario advises 5 to 10 percent over the measured volume for a simple slab and 10 to 15 percent for complex shapes, footings with over-dig or anything with a lot of edges. The calculator defaults to 10 percent because running short during a pour costs far more than a small overage.

Is it cheaper to mix bags or order ready-mix in Toronto?

Builders Ontario puts the crossover at roughly 0.75 to 1 cubic metre. Below that, bags at $6.20 to $7.58 each usually win, because a partial truckload carries its own charge: Canada Building Materials lists $300.00 for a 1.2 to 3 cubic metre load and $400.00 for a single cubic metre.

How thick should a concrete slab be?

Residential slabs in the GTA are commonly poured at 4 inches for a patio or walkway and 5 to 6 inches where vehicles park. Thickness is what drives volume: going from 4 to 6 inches on a 20 by 20 pad adds 66.67 cubic feet, half again as much concrete.

How much does a cubic metre of concrete cost in the GTA?

Canada Building Materials lists 25 MPa at $245.00 per cubic metre on its GTA price list effective January 15, 2026. Builders Ontario puts 2026 residential ready-mix at $175 to $225 delivered, and 2AZ Group publishes $250 to $290 for 25 MPa and $290 to $350 for 32 MPa in the GTA.

Sources

Every figure on this page traces to one of these, re-read on 2026-08-25. Prices are Canadian dollars, before HST. Dataset July 2026.