Canada Concrete Calculator
Concrete Slabs
Concrete Walls
Concrete Stairs
Concrete Footings
Concrete Columns
Concrete Curbs
Amount of Concrete Bags Needed
| Number of 30 kg Concrete Bag(s) | Number of 25 kg Concrete Bag(s) | Number of 20 kg Concrete Bag(s) |
|---|---|---|
| 0 bags | 0 bags | 0 bags |
About This Concrete Calculator
When working with concrete, it's important to be able to calculate the amount you need for your construction project. This concrete calculator will help you determine the volume of concrete you need in cubic meters and cubic feet. It also calculates the number of 30 kg, 25 kg, or 20 kg bags of concrete needed, and an estimated cost for the concrete. You can calculate how much concrete you will need for concrete slabs, walls, stairs, footings, columns, and curbs.
To use this concrete calculator, simply enter the dimensions of what you need concrete for. As an example, you can select the concrete slabs option to calculate how much concrete that you will need for a rectangular concrete driveway. While this construction calculation tool will give you a good estimate of how much concrete to order, it is always best to overestimate slightly. A 5% buffer can account for any spillage, waste, or unexpected circumstances.
While this concrete calculator can be used to estimate your project and can be a starting point, if you have any questions about your specific project, be sure to consult with a professional before proceeding. With a little planning and some basic math, you can easily calculate how much concrete you need for your next project!
Concrete Calculations and Formulas
Every concrete estimate starts with volume. Once you know the length, width, and depth of the space you're filling, the rest is arithmetic. Below are the formulas the calculator uses, so you can check its numbers or work out a project by hand.
Concrete Slab, Wall, and Footing FormulaSlabs, walls, and footings are all rectangular, so they share one formula:
Volume = Length × Width × Thickness
The catch is units. Thickness is almost always smaller than length and width, so people tend to measure it in centimetres while measuring the other two in metres. Before you multiply, put all three measurements in the same unit. To turn centimetres into metres, divide by 100. That gives you a volume in cubic metres, which is how ready-mix concrete is ordered in Canada:
Length (m) × Width (m) × [Thickness (cm) ÷ 100] = Volume in cubic metres
Say you're pouring a slab that is 3 metres long, 3 metres wide, and 10 centimetres thick:
3 × 3 × (10 ÷ 100) = 0.9 cubic metres
If you prefer to work in imperial units, the method is the same, just divide thickness in inches by 12 to convert it to feet:
Length (ft) × Width (ft) × [Thickness (in) ÷ 12] = Volume in cubic feet
A slab 10 feet long, 10 feet wide, and 4 inches thick comes out to 10 × 10 × (4 ÷ 12) = 33.33 cubic feet. Bagged concrete is often labelled in cubic feet, so this is handy for smaller DIY pours. If you need that figure in cubic yards, the unit used in the United States, divide by 27, since there are 27 cubic feet in a cubic yard. That gives about 1.23 cubic yards.
Stairs, Curbs, and GuttersThese shapes look more complicated, but they're just rectangles stacked together. Break the shape into its individual rectangular pieces, find the volume of each with the formula above, then add them up for the total. A flight of stairs, for example, is a series of rectangular steps.
One thing to watch: some of these structures can be built from other materials, which changes the math entirely. If you're framing wooden stairs rather than pouring concrete ones, use a stair calculator instead, since the build method is completely different.
How Thick Should a Concrete Slab Be?
A slab on the ground doesn't span across a gap the way a beam does. It rests on the base underneath, and most of the weight placed on it passes straight down into that base. So the thickness isn't really set by how much load the slab carries. Almost every slab needs a minimum thickness just to be built well and to last, and heavier-duty slabs add thickness on top of that minimum.
The minimum comes from a few practical limits. The pour has to be thick enough to place and finish properly around the aggregate, to cover any wire mesh or rebar, and to resist cracking from shrinkage and minor ground movement. Outdoors in Canada, freeze-thaw usually decides it. As water in the base freezes and heaves, a thin slab cracks.
That's why projects with very different loads land on the same number:
| Use case | Typical thickness |
|---|---|
| Basement floors (protected, lightly loaded) | 75–100 mm (3–4 in) |
| Patios, walkways, garden sheds | 100 mm (4 in) |
| Standard car driveway | 100 mm (4 in) |
| Driveways for heavier vehicles, RVs, or trailers | 125–150 mm (5–6 in) |
| Garage and workshop floors | 100–150 mm (4–6 in) |
The basement floor is the thinnest on the list because it's protected indoors. A patio holds no more weight than that basement slab, yet needs a full 100 mm to survive freeze-thaw. Exposure sets the floor, not load.
Once you're above that minimum, load is what adds thickness, which is why driveways for heavy vehicles and garage or workshop floors run thicker. Keep in mind that thickness alone won't rescue a slab on a poor base. Much of a slab's strength comes from the compacted gravel underneath, so base preparation matters as much as the number you pour to. For anything structural or load-bearing, check your municipal building code or an engineer before you pour.
Concrete Mixes
Once you know how much concrete you need, the next question is what goes into it. Concrete is a blend of cement, sand, and gravel, and the proportions are given as a ratio by volume. A common general-purpose mix is:
- 1 part cement
- 2 parts sand
- 3 parts gravel
This is called a 1-2-3 mix. It lands around 20 to 25 MPa, which suits most residential slabs and footings. Other ratios shift the strength. A leaner 1-2-4 mix has more gravel for each part of cement, so it's weaker, while a richer 1-1-2 mix is stronger. As a rule, the more cement there is relative to the sand and gravel, the higher the strength.
There's an important catch, though. How much water you add matters as much as the ratio of the dry ingredients. Strength is largely governed by the water-to-cement ratio: the less water you use for a given amount of cement, the stronger the finished concrete. That's why a soupy, over-watered mix cures weak and cracks easily even when the cement, sand, and gravel were measured correctly. Add water gradually and stop once the mix is workable but still stiff.
For a small project, bagged pre-mixed concrete is the simplest route. The cement, sand, and gravel come already blended in the right proportions, so you only add water. For a larger pour, ready-mix delivery is usually easier and more consistent, and you order it directly by strength in MPa, such as 25 or 30 MPa, rather than by ingredient ratio.
Where to Buy Concrete in Canada
Once you know how much you need, the next step is deciding where to buy it. For bagged mix, the national chains are the easiest starting point. The Home Depot, RONA, Canadian Tire, and Home Hardware all stock 30 kg bags of ready-to-use concrete, along with cement, sand, and gravel for mixing your own. Local lumber yards and building-supply dealers carry it too, and they often price well on larger quantities.
As of 2026, a basic 30 kg bag of ready-to-use concrete mix starts around $5.50 in lower-cost mainland markets and more commonly runs $6 to $8. Specialty products such as fast-setting, high-strength, or fibre-reinforced mixes cost more, sometimes well into the double digits per bag. Buying by the bag works out to roughly $220 to $350 per cubic metre for the material alone, which is why bags suit small projects but get expensive quickly on a large pour. Prices also vary by region. Shoppers in Atlantic Canada, including Newfoundland, and in remote or northern communities generally pay more because of freight, so seeing $9 or more per bag is common there. Check your retailer's website for current local pricing before you budget.
For anything beyond a few hundred kilograms, ready-mix delivery is usually the better buy. You order it by the cubic metre and by strength in MPa, and in 2026 standard residential concrete of 25 to 32 MPa typically runs about $180 to $210 per cubic metre delivered. Watch for the extras that don't show up in the base price. Most suppliers set a minimum order, often around 3 m³, and charge a short-load fee below it, and there can be surcharges for evening, overnight, or weekend pours, plus environmental and carbon fees. It's worth getting a couple of local quotes and asking what's included before you book.
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