Concrete Calculator
Calculate cubic metres of concrete needed for slabs, footings, columns, and stairs, plus bags and cost.
For columns, enter diameter
Standard slab is 100mm. Footings typically 300-600mm.
Allow 5-10% for waste. More for irregular shapes.
Pre-mixed concrete is typically $250-$350/m3 in Australia
How It Works
Calculates volume in cubic metres based on the shape dimensions (L x W x D for slabs, pi x r^2 x D for columns). Adds the waste factor percentage. Converts to number of pre-mix bags (20kg or 40kg) and estimates cost based on delivery price per cubic metre.
Frequently Asked Questions
How much does concrete cost in Australia?
Pre-mixed concrete costs approximately $250-$350 per cubic metre delivered, depending on location, mix strength, and quantity. Smaller loads (under 2m3) may incur a short-load fee of $50-$150. Pump hire is extra at $150-$300.
How thick should a concrete slab be?
Residential house slabs are typically 100mm (4 inches). Garage slabs are 100-150mm. Driveways should be 100-125mm. Commercial floors are 150-200mm. Reinforcement (mesh or rebar) is required for most applications.
How many bags of concrete per cubic metre?
For 20kg bags of premix concrete: approximately 108 bags per m3. For 40kg bags: approximately 54 bags per m3. Bag concrete is only practical for very small jobs — anything over 0.5m3 is cheaper to order pre-mixed.
How long does concrete take to cure?
Concrete reaches about 50% strength at 3 days, 70% at 7 days, and design strength at 28 days. You can walk on it after 24-48 hours and drive on a driveway after 7 days. Full cure takes 28 days — keep it moist during this period.
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