Concrete Calculator
Estimate how much concrete you need for your project. Quick, simple, and accurate.
Frequently Asked Questions
Why is the thickness input in millimetres (mm)?
Concrete slabs are typically 75–150 mm thick, so millimetres give a more precise measurement. The calculator automatically converts mm to metres for the volume formula.
What diameter should I use for a column?
Common residential column diameters range from 200 mm (0.2 m) to 600 mm (0.6 m). Commercial columns can be 600 mm or larger. Measure the external diameter of the form or casing.
Why do you recommend ordering 5–10% extra?
Concrete can be lost to spillage, uneven ground, over-excavation, and formwork gaps. Ordering a small buffer ensures you don't run short mid-pour, which can compromise structural integrity.
Can I use this calculator for curved or irregular shapes?
This calculator handles standard rectangles and cylinders. For irregular shapes, break the area into simpler sections, calculate each separately, then add them together.
What concrete strength (MPa) do I need?
Common residential uses: 20 MPa for footpaths and shed slabs, 25 MPa for driveways and house slabs, 32 MPa for structural footings. Call us if you're unsure — we'll recommend the right mix.