Concrete Calculator
Concrete volume and bags needed for a slab, with waste allowance.
Enter values
m
m
cm
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Step by step
The formula
volume = length × width × thickness, plus 10% waste
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Frequently asked questions
How many bags of premix per cubic metre?+
This tool assumes a 40 kg premix bag yields about 0.0185 m³ (18.5 litres) of mixed concrete — roughly 54 bags per m³. Check your bag’s label, as yields vary slightly by brand.
Why add 10% waste?+
Uneven ground, spillage and over-excavation almost always consume extra concrete. Ordering 10% more avoids running short mid-pour.
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