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Foundation Calculator
Calculate concrete for foundations
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Result
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What this calculator does
Gives the concrete volume for a strip or trench foundation from trench width, length and depth. For a slab, use the Concrete calculator.
How to use it
- Enter trench width and total run length.
- Enter depth in meters.
- Set waste: trench sides are rarely perfect.
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 | 0.6 |
| Length | m | 10 |
| Depth | m | 1 |
| Waste Margin (%) | % | 10 |
Worked example
Using the default values of this calculator (Width = 0.6 m, Length = 10 m, Depth = 1 m, Waste Margin (%) = 10 %), the calculator returns:
Material volume m³ = 0.6 × 10 × 1 × (1 + 10 / 100)
- Concrete Volume: 6.6 m³
Assumptions and limitations
- Assumes a straight rectangular trench; corners and intersections are not counted twice.
- The calculator gives volume only: it does not judge size, depth or soil suitability, and is not structural design.
Waste, rounding and buying
Order ready-mix by the cubic meter, rounded up. Trench overbreak and uneven bottoms make extra concrete common.
Frequently asked questions
- How is this different from the Concrete calculator?
- Foundation uses trench dimensions with depth in meters; Concrete is for slabs.
- Can it tell me how deep to dig?
- No. Depth must come from a qualified design or local rules.