Concrete Volume Calculator
Estimate the cubic metres of concrete required for slabs, footings, or pathways. Enter the length, width, and depth of the pour to get an instant volume result.
About this calculator
Concrete is ordered by volume, typically in cubic metres (m³). The calculation is straightforward: Volume = length × width × depth. For example, a rectangular slab 4 m long, 3 m wide, and 0.1 m deep requires 4 × 3 × 0.1 = 1.2 m³ of concrete. Always round up when ordering to avoid running short mid-pour. Most ready-mix suppliers add a waste factor of 5–10%, so it is wise to add that buffer to your calculated volume. This calculator is equally useful for driveways, column footings, retaining wall footings, and any other rectangular concrete element.
How to use
Suppose you are pouring a garden path that is 6 m long, 1.2 m wide, and 0.1 m deep. Step 1 — Enter Length = 6 m. Step 2 — Enter Width = 1.2 m. Step 3 — Enter Depth = 0.1 m. Step 4 — The calculator computes Volume = 6 × 1.2 × 0.1 = 0.72 m³. Add a 10% waste buffer: 0.72 × 1.10 ≈ 0.79 m³. Order 0.8 m³ to be safe. Most ready-mix trucks have a minimum delivery of 0.5 m³, so this quantity is well within a standard order.
Frequently asked questions
How do I calculate concrete volume for a circular slab or column footing?
This calculator handles rectangular shapes only. For a circular slab or column, use the formula Volume = π × radius² × depth, where π ≈ 3.1416. Measure the radius (half the diameter) and the thickness of the pour. Multiply those three values together to get cubic metres. You can then apply the same 5–10% waste buffer before ordering.
How much does 1 cubic metre of concrete weigh and how many bags does it equal?
One cubic metre of standard ready-mix concrete weighs approximately 2,400 kg. If you are using 20 kg pre-mix bags, you would need about 120 bags per cubic metre (2,400 ÷ 20). For 25 kg bags the figure drops to around 96 bags. Bagged concrete is only practical for very small pours; ready-mix becomes more economical above roughly 0.5 m³.
What depth should a concrete slab be for a driveway versus a footpath?
A pedestrian footpath typically requires a minimum depth of 75–100 mm (0.075–0.1 m) of concrete. A residential driveway carrying passenger vehicles should be at least 100–125 mm (0.1–0.125 m) thick. Driveways designed for heavy vehicles such as trucks need 150 mm or more, often with reinforcing steel mesh. Always check your local building code, as minimum thickness requirements vary by region.