🏗️ Concrete Calculator
Calculate cubic metres, bags of premix, and cost for slabs, footings, and steps. Includes 10% wastage by default.
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How to calculate concrete volumes
Concrete is ordered by the cubic metre (m³). For small jobs, premix bags are most practical. For large slabs, a ready-mix truck is more economical and gives a better finish.
Typical slab depths
- Garden path / light slab: 75–100 mm
- House slab / driveway: 100–125 mm
- Heavy vehicle / commercial: 150–200 mm
- Footings: 300–600 mm diameter, depth depends on soil type
💡 Rule of thumb: 1 m³ of concrete weighs approximately 2.4 tonnes. A standard 20 kg bag fills about 0.01 m³ — so you need 100 bags to pour 1 cubic metre.