**SEO keyword:** concrete volume calculator
**Meta description:** Estimate concrete quantities for slabs and footings using dimensions, thickness and practical allowances.
Why quantity estimates matter
Concrete orders are usually specified in cubic metres. A reliable preliminary estimate begins with geometry, then accounts separately for waste, overbreak and site conditions.
Rectangular concrete volume formula
For a rectangular prism, volume V = length × width × thickness, with every dimension expressed in metres. If thickness is given in millimetres, divide it by 1,000 first. This produces cubic metres, not kilograms or tonnes.
Worked slab example
For a slab 6 m long, 4 m wide and 150 mm thick, V = 6 × 4 × 0.15 = 3.60 m³. Applying an illustrative 5% ordering allowance gives 3.78 m³. The allowance is a project-specific procurement assumption, not a structural design factor.
Footings and irregular shapes
For separate rectangular footings, calculate each footing volume and sum the results. For stepped or irregular sections, split the geometry into simple volumes. Deduct significant voids only where the contract measurement method permits.
Use a calculator, then check the drawings
The MzStructCalc concrete volume and slab tools can support early quantity checks. Compare results against the latest drawings and confirm thickness, levels and concrete specifications.
**Explore the calculators:** Open the MzStructCalc structural calculators directory.
*Engineering note: These tools provide preliminary calculations, not code-compliant structural designs. Obtain independent professional verification before construction.*