Concrete Calculator Guide: How Much Concrete Do I Need?
Calculate concrete volume for slabs, pads and simple rectangular pours, convert cubic metres to litres and understand what to check before ordering.
Concrete quantity is normally estimated by volume. For a simple rectangular slab or pad, length × width × thickness gives cubic metres. The important part is keeping the thickness unit consistent and treating the result as a planning estimate rather than a guaranteed delivery quantity.
Measure the pour area
Measure the actual length and width of the slab, pad or other rectangular section. If the project has several sections, calculate each section separately and add the volumes.
Convert thickness to metres
This calculator accepts depth in centimetres. Divide centimetres by 100 before multiplying. For example, 10 cm is 0.10 m.
Calculate volume
Multiply length × width × thickness in metres. One cubic metre equals 1,000 litres.
Check real-world ordering factors
Excavation, formwork tolerances, uneven ground, access and supplier minimum loads can affect the practical order quantity. For a real pour, confirm the final quantity with the concrete supplier.
Formula
Concrete volume = length × width × thickness in metres.
Worked example
A 5 m × 4 m slab at 10 cm thickness is 5 × 4 × 0.10 = 2.0 m³, or 2,000 litres.
Common mistakes to avoid
- Using centimetres as metres without conversion.
- Ignoring irregular sections or changes in thickness.
- Treating calculated volume as the exact supplier delivery quantity.
- Forgetting supplier minimum-load or site-access constraints.
Frequently asked questions
How many litres are in one cubic metre of concrete?
One cubic metre equals 1,000 litres.
Does the calculator include waste?
It calculates the geometric volume. Supplier advice should be used for the final order quantity.
Can I use it for footings?
It can estimate a simple rectangular footing, but structural dimensions and reinforcement should follow the project design and applicable requirements.
Use the Concrete Calculator
Enter your project measurements in the calculator, review the result and compare it with the product or supplier information for your specific project.