About this tool Calculate the volume of concrete required for common geotechnical and structural elements. Unlike basic concrete calculators, this tool supports bored piles with overbreak allowance, pad and strip footings, slabs/rafts, and circular columns — the elements site engineers actually deal with.
The calculator automatically applies a 10% waste allowance to all elements, which is the industry-standard ordering margin for ready-mix concrete. For bored piles, a separate overbreak allowance (typically 10–25%) accounts for the oversized bore diameter that occurs in practice, varying by ground conditions.
Results include net theoretical volume, order volume (with waste and overbreak where applicable), and estimated weight based on reinforced concrete at 2,500 kg/m³ per EN 1991-1-1 (Eurocode 1).
How to use this tool 1. Select the element type — choose from slab/raft, circular column, bored pile, strip footing, or pad footing. The input fields will adapt to the selected shape.
2. Enter dimensions — provide length/diameter, width (for rectangular elements), and depth/thickness in metres.
3. Set the quantity — if you have multiple identical elements (e.g. 20 piles), enter the number to get a combined total.
4. Adjust overbreak (piles only) — set the overbreak percentage based on your ground conditions. Stiff clays: 10–15%, granular soils: 20–25%.
5. Read the results — the order volume (including waste and overbreak) is the figure to give your concrete supplier.
Rectangular elements (slabs, footings):
V = length × width × depth × quantity
Cylindrical elements (piles, columns):
V = π × (d/2)² × h × quantity
Order volume includes a 10% waste allowance (industry standard). For bored piles, an additional overbreak allowance accounts for oversized bore diameter. Concrete density: 2,500 kg/m³ for reinforced concrete per EN 1991-1-1 (Eurocode 1, Table A.1).
Pile overbreak guidance Overbreak is the additional concrete consumed when the bored hole is larger than the nominal pile diameter. Typical allowances:
Stiff clays: 10–15% | Firm to soft clays: 15–20% | Granular soils: 20–25% | Weak rock: 15–25%
Always check actual overbreak against theoretical volume during construction. Significantly higher overbreak may indicate ground instability requiring engineering review.
Limitations This tool calculates theoretical volumes for simple geometric shapes only. Complex geometries (tapered piles, stepped footings, irregular slabs) require manual breakdown into individual elements.
The 10% waste allowance is a general ordering margin. Actual wastage depends on site conditions, access, formwork quality, and pour method. For large pours, consult your supplier for their recommended allowance.
Overbreak values are indicative only. Actual overbreak must be monitored during construction by comparing delivered concrete volume against theoretical pile volume. Ground investigation data should inform the overbreak assumption for each site.
Revision history 9 April 2026: Initial release
Disclaimer This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.
Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.
All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.
By using this tool, you accept full responsibility for how you interpret and apply the information provided.
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