Concrete & Masonry
Concrete Volume Calculator
Enter your pour dimensions in metres and millimetres — rectangular or cylindrical — to get the cubic metres of ready-mixed concrete to order, with wastage and an optional VAT-aware cost estimate.
Formula tested · Local units · No sign-up
Project inputs
Enter measurements
Use your preferred units. Results update automatically.
Show the calculation methodFormula, conversions, rounding, and assumptions+
Rectangular pours (slabs, strip footings, walls) use volume = length × width × depth. Cylindrical pours (fence post holes, pad-and-pier bases) use volume = π × (diameter ÷ 2)² × depth. Either is multiplied by the number of identical pours.
UK practice measures plan dimensions in metres and depth in millimetres, so the calculator converts millimetres to metres before multiplying — a 150 mm depth is 0.15 m.
Ready-mixed concrete is sold by the cubic metre; the total is rounded up to the next quarter cubic metre to match typical ordering increments.
Real-world example
Worked example: 5 m × 3 m base, 150 mm thick
- Convert depth: 150 mm = 0.15 m.
- Volume: 5 × 3 × 0.15 = 2.25 m³.
- Add 10% wastage: 2.25 × 1.10 = 2.475 m³.
- Round up to the ordering increment: 2.5 m³.
Order 2.5 m³. At an example price of £100 per m³ plus 20% VAT, that's £250.00 + £50.00 = £300.00.
Before you start
How to measure
- Measure plan dimensions inside the shuttering or trench in metres, and depth in millimetres from the base to finished level — use the deepest reading.
- For strip footings, treat the trench as a long rectangle: length along the trench, width across it.
- For fence post holes, measure the hole diameter and depth and use the cylindrical shape with the number of holes in the 'number of pours' field.
Local guidance
Notes for United Kingdom
- UK suppliers offer both ready-mixed (plant-batched) and volumetric (mixed on site) delivery; volumetric lorries charge for what you pour and suit trench footings where depth varies.
- Footing dimensions for extensions and garden walls are normally agreed with building control or an engineer — this tool estimates volume only.
- VAT at the standard 20% rate applies to most concrete supply; trade quotes are often ex-VAT, so check before comparing.
Quick reference
Volume formulas by pour shape
| Shape | Formula | Typical use |
|---|---|---|
| Rectangular | length × width × depth | Slabs, strip footings, walls |
| Cylindrical | π × (diameter ÷ 2)² × depth | Post holes, piers |
Planning formulas only — trench sides rarely dig perfectly square, so allow wastage.
Good to know
Common mistakes to avoid
- Typing a depth in centimetres into a millimetre field — 15 instead of 150 gives a tenth of the concrete you need.
- Using the diameter instead of the radius when checking the cylinder maths by hand — it quadruples the volume.
- Under-ordering for trench footings: trench sides bulge and bases over-dig, so 10% wastage is sensible.
- Not asking whether the quoted price includes VAT and delivery.
Need help?
Frequently asked questions
How much concrete for a 6 m strip footing, 600 mm wide and 300 mm deep?
6 × 0.6 × 0.3 = 1.08 m³ exactly. With 10% wastage that's 1.19 m³, so order 1.25 m³.
How much for 10 fence post holes, 300 mm diameter and 600 mm deep?
Each hole is π × 0.15² × 0.6 = 0.042 m³, so ten holes are 0.42 m³. With 10% wastage that's 0.47 m³ — order 0.5 m³, or use post-mix bags for this quantity.
Should I choose ready-mixed or volumetric for a footing pour?
Volumetric (mixed on site) suits trench footings because you pay for what's actually poured — useful when trench depth varies. Plant-batched ready-mix suits well-defined shuttered volumes.
Keep planning
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About this calculator
- Written by:
- BuildMeasure Editorial Team
- Technically reviewed by:
- Pending independent technical reviewer (formula unit-tested; see methodology)
- Last reviewed:
- 2026-07-16
- Formula version:
- 1.0.0
- Region reviewed for:
- United Kingdom
- Spotted an error?
- Report a correction
Methodology
- Rectangular pours use volume = length × width × depth × count; cylindrical pours use volume = π × (diameter ÷ 2)² × depth × count. All inputs are converted to SI units (metres) before any arithmetic to avoid unit drift.
- The wastage allowance is applied to the exact volume, then the total is rounded UP to the next 0.25 of the regional ordering unit (cubic yards in the US, cubic metres elsewhere), because ready-mix suppliers typically sell in quarter-unit increments.
- The cost estimate simply multiplies the suggested order quantity by the price you enter, then applies the tax rate you enter. No prices are built in.
- The formula is covered by automated unit tests, including hand-calculated worked examples, and is versioned (see formula version on this page).
Sources & standards
- Unit definitions: Metric units used throughout; 1 m³ = 1,000 litres.
- Ordering increments: Quarter-cubic-metre increments are typical for UK ready-mix; confirm with your supplier.
This tool provides a material estimate for planning purposes only. It is not a quotation, and it does not size reinforcement, check ground conditions, or replace professional structural advice. Confirm quantities and mix specification with your supplier before ordering.