Concrete Volume & Bag Calculator
Calculate cubic meters and 20kg/40kg premix bag counts for slabs.
Last reviewed by the myCalculator Editorial Team
Input Parameters
Calculation Results
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Formula & How Concrete Volume & Bag Calculator Works
Concrete volume is length × width × depth, converted to cubic metres, plus an allowance for waste, spillage and uneven ground. A slab 6 m long, 4 m wide and 100 mm thick is 6 × 4 × 0.1 = 2.4 m³. Adding 10% for waste gives 2.64 m³, so you would order about 2.7 m³. Ready-mix is sold by the cubic metre and most suppliers have a minimum order, and small jobs can use bagged mix instead. The thickness, strength grade and reinforcement of a slab depend on its use and ground conditions, so confirm the specification with an engineer or the relevant building standard before you pour.
- Enter Slab Length (m): Input your target parameter value.
- Enter Slab Width (m): Input your target parameter value.
- Enter Slab Depth / Thickness (cm): Input your target parameter value.
- Enter Wastage Reserve (%): Input your target parameter value.
- Apply Formula: Calculate using
Volume = Length × Width × (Depth / 100) × 1.10. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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Are you using our calculation results for a university assignment, research paper, or academic report? Use the auto-generated citations below to accurately reference this tool in your bibliography.
MyCalculator.com.au. (2026). Concrete Volume & Bag Calculator. Retrieved October 24, 2026, from https://www.mycalculator.com.au/calculators/engineering/concrete
MyCalculator.com.au. (2026) 'Concrete Volume & Bag Calculator'. Available at: https://www.mycalculator.com.au/calculators/engineering/concrete (Accessed: 24 October 2026).
Frequently Asked Questions (FAQs)
How many 20kg bags make 1 cubic meter?
Approximately 108 to 110 bags (20kg) equal 1 m³ of wet concrete.
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Authoritative Standards & Verified Reference Citations
Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
Australian Standards including AS/NZS 3000 (Wiring Rules), AS 3600 (Concrete Structures), and AS 4100 (Steel Structures).
Accreditation and technical guidelines for civil, structural, mechanical, and electrical engineering.
Dedicated Australian home loans, borrowing capacity, mortgage repayments & refinance modeling.