Concrete calculator
Work out how many cubic metres of ready-mix concrete you need for slabs, strip footings, pad foundations and columns. Enter your dimensions, add a wastage allowance and request a trade quote with same-day or next-day delivery.
Concrete needed
3.15 m³
Includes 5% wastage allowance.
Tip: ready-mix concrete is usually ordered in whole cubic metres. Round up to the nearest m³ when calling for a quote.
How the concrete volume calculator works
Enter the length, width and depth of your slab, footing or column in metres and the calculator returns the net volume in cubic metres. Add a wastage percentage (typically 5–10% for slabs and 10% for footings) to cover over-excavation, spillage and pump or wheelbarrow losses. The result is a ready-to-order figure for C20, C25, C30, GEN1, GEN3, RC35 or foamed concrete.
Slabs, footings and column sizes
A standard 100 mm garage slab on a 4 m × 6 m base needs roughly 2.4 m³ of concrete. Strip footings for a single-storey extension are typically 450 mm wide × 300 mm deep, and a 300 mm square column filled to 2.5 m takes around 0.23 m³. Adjust your inputs to match the engineer's drawing and remember to include the wastage factor before you order.
Ordering tips from our trade counter
- Round up to the nearest 0.25 m³ — short loads often attract a part-load fee.
- Allow site access for an 8 m³ truck and a clear pour area before booking.
- For pours over 6 m³ consider a boom pump to cut barrow time and labour cost.
- Confirm the mix strength (C20/C25 etc.) and aggregate size with your engineer or building control.
Common projects
Quick reference quantities for the jobs we get asked about most. Enter your own measurements in the calculator above for an exact figure.
100 mm garage slab
A 4 m × 6 m base needs roughly 2.4 m³ of ready-mix concrete before wastage.
Strip footing run
450 mm wide × 300 mm deep for a 10 m run needs about 1.35 m³ of concrete.
300 mm square column
A 300 mm × 300 mm column filled to 2.5 m takes around 0.23 m³.
Pad foundation
A 1 m × 1 m × 500 mm pad foundation needs roughly 0.5 m³ of concrete.
Shed base
A 2 m × 2 m × 100 mm shed base needs about 0.4 m³ plus a small wastage allowance.
Frequently asked questions
- How do I calculate concrete volume?
- Multiply length × width × depth in metres. The result is the volume in cubic metres (m³).
- How much wastage should I add?
- Allow 5–10% for slabs and 10% for footings and columns to cover spillage, over-excavation and pump losses.
- What concrete mix do I need?
- C20 or C25 is typical for domestic slabs and footings. C30/C35 is used for structural work. Always confirm the mix strength with your engineer or building control.
- Can I order less than 1 m³?
- Most ready-mix suppliers have a minimum order and may charge a part-load fee for small volumes. It is often more cost-effective to combine pours.
- How many 25 kg cement bags are in 1 m³ of concrete?
- For site-mixed concrete, roughly 12–14 bags of 25 kg cement are needed per cubic metre, depending on the mix ratio and aggregate size.