Concrete Calculator (volume)
Volume of concrete for a slab from its length, width and thickness.
Result
Volume (m³)
2.000
Volume (litres)
2,000
How it works
Concrete for a slab is pure volume: length × width × thickness. The trap is units — thickness is given in centimetres while the other two are in metres, so convert before multiplying. A 5 × 4 m slab of 10 cm gives 5 × 4 × 0.10 = 2 m³. Order more than the bare calculation. Professionals add 5–10% for spillage, uneven subgrade and the concrete left in the mixer or pump line. Coming up half a cubic metre short mid-pour is a serious problem: a cold joint forms and the slab loses strength. Two practical notes: ready-mix is sold by the cubic metre and usually has a minimum order, while bagged mix states its yield per bag (a 35 kg bag typically yields around 15–17 litres, so roughly 60 bags per cubic metre). Confirm the yield printed on your bags before converting.
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Frequently asked questions
How do I calculate concrete volume?
Multiply length × width × thickness (all in metres). For a 10 cm slab use 0.10 m.
How many m³ for a 5×4 m slab at 10 cm?
5 × 4 × 0.10 = 2 m³.
How much extra concrete should I order?
Add 5–10% to the calculated volume for spillage, an uneven base and material left in the mixer. Running short mid-pour creates a weak cold joint — over-ordering slightly is far cheaper than that.
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