Free tool
Concrete calculator
How much to order for a slab, footing, pad or round column — in cubic metres and cubic yards, with your own waste allowance. Measure in metres or feet and give the thickness in millimetres or inches, because that is how the numbers usually arrive.
Order this much
2.64 m³
3.45 yd³ · 93.2 ft³ · measured 2.4 m³ before waste
A quantity tool, not a design one. It converts the dimensions you enter into a volume and adds the waste you choose. It does not decide how thick a slab should be, which mix to use or where reinforcement goes — those depend on loads, ground conditions and your local building code, and they belong to whoever is responsible for the structure.
The arithmetic, in full
Slab, footing or pad. Volume = length × width × thickness. A 6 m × 4 m pad at 100 mm is 6 × 4 × 0.1 = 2.4 m³. At 10% waste you would order 2.64 m³.
Round column or pier. Volume = π × (diameter ÷ 2)² × height. A 300 mm column 3 m high is π × 0.15² × 3 = 0.212 m³. Note it goes with the square of the diameter, so a column 50% wider needs more than twice the concrete.
Imperial. A 10 ft × 10 ft slab at 4 in is 100 ft² × ⅓ ft = 33.33 ft³, which is 1.23 yd³ — divide cubic feet by 27.
Bags. Bags = volume in litres ÷ the yield on the bag, rounded up, because a part bag is still a bag you have to buy.
Frequently asked questions
- How do I calculate how much concrete I need?
- Volume is length × width × thickness for a slab, and π × (diameter ÷ 2)² × height for a round column. Keep the units consistent, then add the waste you want to carry. The calculator above does the unit conversion so you can measure a slab in feet and specify it in inches, which is how most people actually have the numbers.
- How many cubic yards is a cubic metre?
- One cubic metre is about 1.308 cubic yards, because a yard is 0.9144 m exactly and the conversion is cubed. Going the other way, a cubic yard is about 0.765 m³. Canadian ready-mix is usually ordered in cubic metres and US ready-mix in cubic yards, so the calculator shows both.
- How much waste should I add to a concrete order?
- That is a judgement about your site, not a fixed number, which is why it is an input rather than a default we assert. Spillage, an uneven sub-base and over-excavated footings all push it up. The calculator starts at 10% because it has to start somewhere — change it to whatever your own pours have taught you.
- How many bags of concrete are in a cubic metre?
- It depends on the bag, so enter the yield printed on yours. A bag's yield is a volume, often given in litres: divide 1,000 by that figure for bags per cubic metre. We do not publish one number because yields differ between manufacturers and between mixes, and a wrong one here is a wasted trip.
- When is ready-mix better than bags?
- Mostly a question of effort rather than price. Past roughly half a cubic metre you are mixing a lot of bags by hand, and the calculator says so once you enter a yield. Below that, bags avoid a delivery minimum and a truck waiting.
- Does this tell me how thick my slab should be?
- No, and deliberately so. This is a quantity tool: you supply the dimensions and it returns a volume. Thickness, mix strength and reinforcement are design decisions that belong to whoever is responsible for the structure, and they depend on loads, soil and your local code.
Getting it into a priced estimate
A volume is the easy half. Turning it into a quote means a unit cost, a markup and the right provincial tax, then carrying that number through to the job budget so you can see whether the pour came in where you priced it.
Also useful: markup vs margin, profit margin, and the free Canadian estimate template.