Estimate whole concrete-mix bags from slab, area, post-hole, or known-volume measurements using the manufacturer’s stated yield per bag.
Calculate project volume, add one planning allowance, divide by the manufacturer yield per bag, and round up to a whole bag.
Bag weight alone does not define mixed-concrete yield. The initial 0.5 ft³ value is an editable planning example, not a universal yield; check the selected product label and enter its stated yield.
volume = length × width × thickness × quantityvolume = area × thickness × quantityvolume = π × (diameter ÷ 2)² × depth × quantityplanning volume = base volume × (1 + extra percentage ÷ 100)bags to buy = ceil(planning volume ÷ manufacturer yield per bag)effective project volume = bag count × yield ÷ (1 + extra percentage ÷ 100)A 10 × 10 ft slab, 4 in thick, contains about 33.33 ft³. With 10% extra and an illustrative user-entered 0.5 ft³ yield, the exact requirement is about 73.33 bags, so buy 74.
A known 20 ft³ requirement becomes 22 ft³ with 10% extra. At an illustrative user-entered 0.5 ft³ per bag, buy 44 bags.
Four 12 in diameter, 36 in deep post holes contain about 9.4248 ft³. With 10% extra and an illustrative 0.5 ft³ yield, the exact requirement is about 20.7345 bags, so buy 21.
A 1.5 m³ requirement becomes 1.65 m³ with 10% extra. At an illustrative user-entered 0.015 m³ per bag, buy 110 bags.
Enter the mixed-volume yield printed on the exact product rather than estimating yield from bag weight.
Small depth changes materially affect slab volume.
The allowance increases concrete volume before bag division; it is not applied again to bag count.
For large quantities, use the related Concrete Calculator to compare project volume and ready-mix pricing without assuming a cutoff.
All measurements are converted to cubic meters internally without rounding. Results are then displayed in cubic feet, cubic yards, cubic meters, and liters.
Rectangle mode multiplies length, width, and thickness. Area mode uses the shared area-to-volume helper and supports ft², yd², and m².
Post holes use diameter and depth with the shared cylinder helper. Quantity multiplies identical holes before extra is applied.
Manufacturer yield is the purchase basis and remains editable for every bag label. The 0.5 ft³ starting value is only an editable example. Published yields vary across package sizes and products, while bag weight is informational only.
Conversions use the shared volume system. Bags per cubic yard are dynamically derived from the entered yield; no fixed bag-per-yard assumption is used.
Reverse mode shows nominal mixed volume from a whole bag count and the effective project requirement after reserving the selected planning allowance.
Cost is whole bags multiplied by price per bag. Optional dry weight is bag count multiplied by entered package weight and never affects concrete volume.
Divide waste-adjusted project volume by the manufacturer yield and round up.
Multiply slab length, width, and thickness, then divide the planned volume by yield per bag.
It depends on yield. The calculator divides one cubic yard by your entered yield.
Use the mixed-volume yield printed by the manufacturer; the initial calculator value is only an editable example.
No. Weight alone does not universally determine mixed yield.
Calculate each cylindrical hole volume, multiply by quantity, add extra, and divide by yield.
Choose an allowance appropriate to measurement uncertainty, spillage, and site conditions.
Thickness and product yield are required. At 4 in thick, 10% extra, and an illustrative 0.5 ft³ per bag, buy 74 bags; replace that yield with the selected product’s label value.
Use the shared volume conversion; one cubic yard equals 27 cubic feet.
Multiply 50 by the manufacturer yield. Reverse mode performs this calculation.
Yes. Metric lengths, square meters, cubic meters, and liters are supported.
No. Follow the product manufacturer’s water instructions.
No. It does not infer PSI or MPa strength or select a concrete product.
This manufacturer data sheet lists different approximate yields for different package sizes of one concrete-mix product, illustrating why the selected product’s stated yield must be used.