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Concrete Calculator

Calculate concrete volume for slabs, footings, columns and circular slabs.

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Waste & Bags
%
Check your bag's packaging — a 20kg bag is commonly around 0.0086 m³.
Concrete Needed
0 m³

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    Order the right amount of concrete, every time

    Choose your shape — slab, footing, round column or circular slab — enter the dimensions, and get the volume in cubic metres and cubic yards, plus an estimated bag count if you're using bagged mix.

    This tool provides quantity estimates only and does not replace engineering advice. For structural pours, always confirm depth, reinforcement and mix design with a qualified engineer.

    How to use it

    • Select the shape that matches your pour.
    • Enter dimensions in whatever unit is easiest — mix and match mm, cm, m, inches, feet or yards.
    • Add a wastage allowance and, if using bags, the yield per bag from the packaging.

    The formulas

    Slab / Footing = Length × Width × Thickness (or Depth) Column / Circular Slab = π × (Diameter ÷ 2)² × Height (or Thickness) Volume With Waste = Volume × (1 + Wastage %) Bags Needed = ROUND UP(Volume With Waste ÷ Bag Yield)

    Worked example

    A 4m × 3m slab at 100mm thick is 1.2 m³. With 5% wastage that's 1.26 m³ — about 1.65 cubic yards, or roughly 147 bags at 0.0086 m³ per bag.

    This tool provides general calculations only and does not constitute financial, tax, legal or professional advice. Actual material requirements can vary due to waste, installation method, site conditions, manufacturer specifications, local codes and measurement accuracy. Always confirm quantities with your supplier before ordering.

    Frequently Asked Questions

    Does this account for reinforcement or engineering requirements?

    No. This is a quantity estimate only — always confirm depth, reinforcement (mesh/rebar) and mix design with a qualified engineer for structural work.

    How much wastage should I allow for concrete?

    5% is a common allowance for formed pours. Increase it for uneven ground, hand-mixing, or pours where over-ordering is expensive to fix.

    What if I'm using ready-mix instead of bags?

    Use the cubic metre or cubic yard figure directly with your ready-mix supplier — the bag count is only relevant if you're using bagged mix.