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Concrete volume and bag estimator

Estimate the concrete to order for a slab, footing, or round column, including waste.

Last reviewed: October 27, 2026

Inputs

ft

ft

in

%

Concrete shape diagramLengthWidthDepth

Results

Net volume
—
Volume with waste
—
Ready-mix quantity
—
60 lb bags
—
80 lb bags
—

Reference data: Nominal bag yields are based on the published yield guidance for QUIKRETE Concrete Mix product data. Verify the exact product and local availability.

How it works

Rectangular slabs and footings use length × width × depth. Round columns use the area of a circle multiplied by height. The waste factor is applied after the net volume.

Vrectangular=LWDV_{rectangular}=LWD
Vcolumn=π(d2)2hV_{column}=\pi\left(\frac{d}{2}\right)^2h
Vorder=Vnet(1+waste100)V_{order}=V_{net}\left(1+\frac{waste}{100}\right)

Assumptions and limitations

Bag counts use stated nominal yields of 0.45 ft³ for a 60 lb bag and 0.60 ft³ for an 80 lb bag. Actual yield varies with product, water, consolidation, and field conditions. Do not use this estimator for mix design, structural capacity, or truck ordering without confirming supplier requirements.

Worked example

A 10 ft × 10 ft slab at 4 in thick has a net volume of 33.33 ft³. With 10% waste, the estimate is 36.67 ft³, or 1.36 yd³. The same estimate rounds up to 62 nominal 80 lb bags.

Frequently asked questions

Should I order exactly the calculated ready-mix quantity?
No. Confirm dispatch increments, access, placement rate, and a project-appropriate waste allowance with the supplier.
Why does a round column hide the length field?
A round column is defined here by diameter and height, so a separate length is not needed.

Related tools

Simply supported beam calculator
Rebar weight and quantity calculator

Important disclaimer

For estimation and education, verify with a licensed engineer.