Garage slab
5 × 4 m slab, 12 cm thick, 5 % waste: 2.52 m³ to order; at 350 kg/m³, 882 kg of cement, i.e. 26 bags of 35 kg.
Concrete calculator
Estimate how much concrete to order for a slab, a footing or columns, including a waste margin. PRAXAO also works out the cement (and number of bags), sand, gravel and water from a mix you can adjust to your recipe or your supplier.
Result
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Results are provided for information. Check tax rates and legal requirements that apply to you.
How to use it
- Choose the element: slab, footing, rectangular or round column.
- Enter the dimensions in metres and the number of identical elements.
- Set the waste margin (5–10 % is common).
- Check the cement dosage, bag size and mix per m³, then read the volume and materials.
Examples
Four round columns
30 cm diameter, 3 m high: 0.848 m³ before waste.
Frequently asked questions
How do I calculate a concrete volume?
Length × width × thickness, in metres. A 5 × 4 m slab, 0.12 m thick, needs 2.4 m³, before adding a waste margin.
Which cement dosage should I use?
It depends on the element and the required strength. Follow your plans, the engineer’s specification or the product data sheet; PRAXAO uses the dosage you enter.
Are the sand and gravel quantities exact?
They are estimates from the mix per m³ you set. Densities and recipes vary; confirm with your supplier, especially for ready-mixed concrete.
Why add a waste margin?
Uneven ground, formwork deformation and spillage consume extra concrete. Running short during a pour is far more costly than a small surplus.
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