About the Concrete Slab Calculator
Concrete, mesh and formwork for a floor slab, driveway or patio, with the bag count and cost.
Also known as: slab concrete calculator, driveway concrete, patio concrete, floor slab volume.
How to use this calculator
- Enter length, width, thickness, waste allowance and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
Volume = area × thickness × (1 + waste)
Worked example
Using the values pre-filled in the calculator above:
- Length = 6 m
- Width = 4 m
- Thickness = 125 mm
- Waste allowance = 7 %
- Mix ratio: 1 : 1.5 : 3 (M20) — 20 MPa — slabs and footings
- Price per m³ = 140
the calculator returns:
- Concrete required: 3.21 m³
- Slab area: 24 m²
- Cement bags (50 kg): 26
- Sand: 1.348 m³