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Concrete & construction

Concrete Volume Calculator

Volume of concrete for a slab, a footing, a column or a set of steps, in cubic yards and cubic feet.

Your numbers

ft
ft
in
in
ft

Result

Cubic yards 3.0
Cubic feet 80.0
Per item 3.0 Cubic yards
60 lb bags if mixing by hand 178
That is 3.0 cubic yards, 80.0 cubic feet. By hand it would take about 178 sixty-pound bags, which is why anything past half a yard is usually ordered ready-mixed.

Concrete is ordered by the cubic yard and delivered in fixed increments, so the figure you order is always rounded up. Most crews add 5% to 10% for spillage, uneven subgrade and over-excavation; running short mid-pour is far more expensive than a little waste. A 60 lb bag yields roughly 0.45 cubic feet, so bag counts rise very quickly with volume.

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Questions

About this calculator

When is bagged concrete sensible?

Under about half a cubic yard. Beyond that the number of bags, the mixing time and the risk of cold joints between batches all argue for a truck.

Does the shape really change the order much?

Round footings catch people out, because area goes with the square of the radius. Doubling a column diameter quadruples the concrete.

The formula

slab = L x W x depth/12; round = pi x r^2 x height; yards = cubic feet / 27

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