Concrete Slab Calculator
Estimate concrete volume for a rectangular slab, including wastage.
Result
- Net concrete
- 6.000 m³
- Order quantity
- 6.300 m³
FREE CONCRETE CALCULATOR
Concrete Slab Calculator
Estimate the concrete volume required for a rectangular slab using length, width, slab thickness and a wastage allowance. The calculator gives a quick cubic-metre quantity for early planning and supplier discussions.
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When this tool is useful
Practical preliminary checks
- Early quantity checks for residential slabs and small concrete areas
- Comparing slab dimensions before requesting supplier pricing
- Allowing for a practical percentage of waste before ordering
- Checking whether a quoted concrete quantity is broadly consistent with the slab dimensions
How it works
The calculator converts slab thickness from millimetres to metres, then multiplies length × width × thickness. The selected wastage percentage is added to the base volume to provide an ordering allowance.
Important estimating note
Actual concrete quantities can change because of beams, thickenings, rebates, set-downs, footing details, site conditions and the structural design. Always confirm the final order from the approved drawings and engineering.
Frequently asked questions
How do I calculate concrete for a slab?
Multiply slab length by width by thickness in metres to get cubic metres, then add an allowance for waste. Structural beams and thickenings need to be calculated separately unless they are included in the dimensions.
What wastage should I use for concrete?
The appropriate allowance depends on the pour, site access, formwork and ordering conditions. A small percentage is commonly used for preliminary planning, but the final order should be confirmed with the concreter, engineer and supplier.
Does this calculator include slab beams and edge thickenings?
No. The standard slab calculation is a simple rectangular volume. Beams, edge thickenings, piers and other structural details should be added from the engineering drawings.
Related EBC guidance
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