Work out how much concrete to order for a slab, footing, wall, post holes or stairs. Add several pours together, then send the numbers to us with your quote request.
How to use it
- Measure the inside of the forms. For a slab, use the finished thickness, not the depth of the excavation.
- Several parts to one pour, like footings plus post holes? Add each one, and the calculator adds them up.
- Stairs are worked out as solid steps, filled underneath. If yours sit on a sloped slab, ask us.
- Island ready-mix plants sell by the cubic metre. Round up when you order; your supplier will confirm the amount.
Common questions
How much extra concrete should I order?
Most people add 5 to 10%. Use 10% for slabs on uneven ground, footings in dug trenches, or anything you can't measure exactly. Running short mid-pour is far worse than a little left over.
How many bags is that?
A 30 kg bag of concrete mix makes about 0.014 m³, so one cubic metre is roughly 71 bags. Past about half a cubic metre, ready-mix is usually much less work, and a line pump gets it to the forms without wheelbarrows.
Cubic metres or cubic yards?
One cubic yard is about 0.76 m³. Ready-mix plants on the Island quote in cubic metres, so that's the number to give your supplier.
Do you supply the concrete?
No. You order it from your ready-mix supplier and tell them it's being pumped. We bring the pump and line, and coordinate the timing with them.
Pour coming up?
Send the address, the volume and your pour date. We'll check access and line length and send you a quote.
Last updated October 29, 2026