Concrete Calculator

Estimate cubic yards of concrete for a rectangular slab.

Ordering concrete

This calculator provides a volume estimate. Actual orders can vary because of subgrade conditions, form dimensions and supplier minimums. Verify your final quantity before ordering.

Concrete slab formula

For a rectangular slab, multiply length × width × thickness to get volume. Because thickness is usually measured in inches, this calculator converts it to feet, then converts cubic feet to cubic yards by dividing by 27. The waste allowance is added after that conversion.

Common slab thickness examples

A 4-inch slab is common for many residential flatwork projects, but the correct thickness depends on the project, loads, soil, reinforcement and local requirements. Driveways, structural slabs and other load-bearing work may require different specifications.

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