Concrete volume calculator
Calculate the concrete volume in cubic metres for a slab, footing or beam, and add a waste allowance for the order.
How it is calculated
Net volume = length × width × thickness, all in metres. Volume to order = net volume × (1 + waste ÷ 100).
Worked example
Slab 5 m × 4 m × 0.10 m: net = 2.00 m³. With 10 % waste, order 2.20 m³.
Steps
- Measure the length, width and thickness in metres.
- For a footing or beam, multiply by the depth or section size instead.
- Add a waste allowance (5 % to 10 % is common), then round up to the truck size.
Frequently asked questions
How much waste should I add?
Usually 5 % for flat slabs on good forms, and 8 % to 10 % for irregular shapes or pumped concrete.
Does this subtract openings?
No. Subtract the volume of openings yourself if they are large.
Can I convert to bags of cement?
Yes, but the mix ratio decides the count. Use your mix design, not a generic number.
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References
Volume = L × W × T; waste allowance practice from ACI 301 (structural concrete specification) and typical site practice.
Estimates for information only. Verify critical values with a qualified engineer or your supplier standards.