Concrete Volume Calculator (Cubic Yards and Bags)

Length × width × thickness, plus waste. Thickness is the depth of the pour (inches or millimetres). Bags use 0.45 ft³ per 60 lb bag and 0.60 ft³ per 80 lb bag, rounded up to whole bags.

Inputs

Units

Results

Volume: 36.667ft³
Volume: 1.358yd³
60 lb (27 kg) bags: 82
80 lb (36 kg) bags: 62

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

Example products

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Calculation method

A 10×10 ft slab 4 in thick is 33.3 ft³ (1.23 yd³) before waste; with 10% waste it is 36.7 ft³, or 82 bags of 60 lb or 62 bags of 80 lb. Ten percent waste is common for small pours. Metric mode shows m³, but the bag counts still use the US 60/80 lb yields. For 25 kg bags, divide the m³ result by the yield printed on the bag, usually about 0.012 m³ (12 L).

Exact formula

cu ft = L × W × (thickness_in / 12) × (1 + waste/100). cu yd = cu ft / 27. 60 lb bags = ceil(cu ft / 0.45); 80 lb bags = ceil(cu ft / 0.60). Metric volume is the same pour in m³.

Ready-mix vs bags

Above about 1 yd³ (0.76 m³), or 45 bags of 80 lb, get a ready-mix quote: mixing that many bags by hand is a long day. Small loads often carry a short-load fee, so compare delivered prices. Use the yardage output to quote a truck.

Frequently asked questions

How many 80 lb bags in a cubic yard?

45, because 27 / 0.60 = 45, or 60 bags of 60 lb. The tool adds the waste first, then rounds up to whole bags.

Can I enter a footing as a long narrow slab?

Yes. Use length × width × thickness of the trench.

Why two volume outputs?

Bags and small pours are figured in cubic feet, while US ready-mix plants sell by the cubic yard. In metric mode both lines show the same pour in m³, the unit European suppliers price by.