Concrete Calculator
Calculate concrete volume for slabs, footings, and columns. Get results in cubic yards (US), cubic metres (UK/AU), and bag counts for common bag sizes worldwide.
Concrete Mix Standards by Country
The concrete you order differs by country — not just in units, but in how strength is specified.
| Country | Standard | Bag Sizes | Volume Unit | Typical Slab Depth |
|---|---|---|---|---|
| 🇺🇸 United States | ACI 318 (psi strength) | 60 lb, 80 lb | Cubic yards (yd³) | 4 in (100 mm) |
| 🇬🇧 United Kingdom | BS 8500 (MPa, e.g. RC25) | 20 kg, 25 kg | Cubic metres (m³) | 100 mm (4 in) |
| 🇦🇺 Australia | AS 3600 (N20, N25, N32) | 20 kg, 25 kg | Cubic metres (m³) | 85–100 mm |
| 🇨🇦 Canada | CSA A23.3 (MPa) | 30 kg, 25 kg | Cubic metres (m³) | 100 mm (4 in) |
| 🇩🇪 Germany | DIN EN 206 (C20/25) | 25 kg | Cubic metres (m³) | 10–15 cm |
Frequently Asked Questions
How much does a 60 lb bag of concrete cover?
A 60 lb (27 kg) bag yields approximately 0.45 ft³ (0.013 m³). For a 4-inch slab, that covers about 1.35 ft². An 80 lb bag covers ~1.8 ft² at 4 inches. For large pours (over 1 cubic yard), ordering ready-mix concrete is usually more economical than bags.
What concrete mix ratio should I use?
Standard ratios (cement:sand:aggregate): General purpose 1:2:4, Footings/foundations 1:3:6, Structural/reinforced 1:1.5:3. Bagged premixes like Quikrete (US) and Postcrete (UK) are pre-blended — just add water. In Australia, specify concrete by N-class (N20, N25, N32) from a ready-mix supplier.
When should I use a concrete truck vs bags?
For pours over 0.5 cubic yards (0.38 m³), ready-mix concrete is typically more economical. In the US, concrete trucks typically deliver a minimum of 1 cubic yard. In the UK and Australia, mini-mix lorries can deliver as little as 0.25 m³. The price crossover point varies by region and current cement prices.