Metric Concrete Calculator

How it's calculated

Concrete is sold by volume in cubic metres (m³). Measure the space you are filling, work out its volume, add wastage, then convert to bags or a premix order.

Volume by shape

Slab / footing  =  length × width × thickness

Cylinder (column / post)  =  π × (diameter ÷ 2)² × height

All dimensions are entered in millimetres. Pouring more than one identical item? Set quantity and we multiply the volume.

Wastage

Real sites lose concrete to spillage, an uneven sub-base and over-dug holes. 10% is standard. Bump it up for rough ground or drop it for tidy formwork. Your total to order is volume × (1 + wastage%).

Bags or premix

A 20 kg bag yields about 9.8 litres (0.0098 m³), so roughly 102 bags fill a cubic metre. We round bags up. Premix from a truck is sold in 0.1 m³ steps. Below 0.5 m³, bags usually avoid short-load fees and suit smaller DIY pours.

Cost estimates use indicative metro prices. Confirm quantities and prices with your supplier.