How the concrete calculation works
Concrete volume (m³) = length (m) × width (m) × thickness (cm) ÷ 100.
Worked example
A 5 m × 4 m slab at 10 cm thick is 20 × 0.10 = 2.00 m³ of concrete.
Guide: using this calculator accurately
For the full explanation, worked examples, measurement tips and FAQs, read the Concrete Guide →.
How to measure a concrete slab
Measure the finished length and width, then determine the design thickness. For a uniform slab, volume is simply area multiplied by thickness.
Why thickness is important
A small change in slab thickness can significantly change the concrete volume. Use the specified thickness for the project rather than estimating from appearance.
Ordering ready-mix concrete
Suppliers may have minimum order quantities, truck capacities and delivery constraints. Add an appropriate allowance for uneven excavation and spillage, and confirm the final order with the supplier.
Concrete volume versus structural design
This calculator estimates volume only. Reinforcement, sub-base, joints, drainage, formwork and structural requirements are separate decisions.
Common concrete-calculation mistakes
Mixing centimetres and metres is a frequent error. This calculator explicitly asks for thickness in centimetres and converts it to metres.
Frequently asked questions
How many litres are in a cubic metre?
One cubic metre equals 1,000 litres.
Should I add extra concrete?
Real sites are rarely perfectly uniform. A practical ordering allowance may be needed, but the correct percentage depends on excavation accuracy and project conditions.
Can this calculate footings?
It can calculate a simple rectangular footing volume. Actual footing design and reinforcement should follow the applicable building requirements and professional plans.