Calculate how much concrete (in cubic metres and bags) you need for slabs, footings, columns, and steps. Based on Australian pre-mix bag sizes.
| Item | Value |
|---|
Concrete is the most widely used construction material in Australia. Standard residential slab thickness is 100mm (10cm). Driveways typically use 100–125mm. Footings are usually 200–300mm deep and 400–600mm wide depending on soil and load.
| Bag size | Volume (wet) | Coverage (100mm slab) |
|---|---|---|
| 20kg bag | ~0.010 m³ | ~0.10 m² at 100mm |
| 25kg bag | ~0.012 m³ | ~0.12 m² |
| 40kg bag | ~0.020 m³ | ~0.20 m² |
For volumes over 0.5 m³, ordering ready-mix concrete (delivered by truck) is usually more economical. In Australia, a standard concrete truck carries 6–8 m³. Most suppliers have a minimum order of 0.2–0.5 m³ with a short-load surcharge.