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Concrete Calculator
Calculate concrete volume in cubic meters
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Result
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What this calculator does
Gives the volume of concrete for a flat slab, pad or path from width, length and thickness. Use it for slabs on the ground; for trenches see the Foundation calculator.
How to use it
- Enter slab width and length in the same unit system.
- Enter the thickness (depth) in meters.
- Set a waste margin for spillage and uneven sub-base, then read the volume in cubic meters.
Formula
Material volume m³ = Width × Length × Depth × (1 + Waste Margin (%) / 100)
Formulas are shown in metric units, exactly as the calculator computes them. Imperial entries are converted to metric first. Waste is applied as a multiplier (1 + waste/100).
Areas are in m² and volumes in m³.
Variables
| Variable | Unit | Default |
|---|---|---|
| Width | m | 4 |
| Length | m | 5 |
| Depth | m | 0.15 |
| Waste Margin (%) | % | 10 |
Worked example
Using the default values of this calculator (Width = 4 m, Length = 5 m, Depth = 0.15 m, Waste Margin (%) = 10 %), the calculator returns:
Material volume m³ = 4 × 5 × 0.15 × (1 + 10 / 100)
- Concrete Volume: 3.3 m³
Assumptions and limitations
- Assumes a perfectly flat, level slab with uniform thickness.
- The result is volume only; it does not give a mix, strength class or reinforcement.
Waste, rounding and buying
Ready-mix is ordered by whole or half cubic meters, so round up. Order extra if the sub-base is uneven.
Frequently asked questions
- How thick should a slab be?
- That depends on load and ground. The calculator only converts a thickness you choose into volume; ask a qualified professional for the thickness.
- Why add waste to concrete?
- Sub-base is rarely perfectly level and some concrete is lost in pumping and formwork gaps.