Slab Volume Calculator

Cubic yards are the standard unit of measurement for ordering ready-mix concrete delivered by a truck. There are 27 cubic feet in one cubic yard. While you measure your project in feet, you order the concrete in yards.

This calculator bases the estimate on standard 80 lb. bags of concrete mix, which typically yield about 0.60 cubic feet of concrete. The number is rounded up to the nearest whole bag. Always check the yield printed on the specific brand of concrete bags you purchase, as it can vary slightly.

Yes, it's always a good idea to order about 10% extra concrete to account for uneven subgrade, spills, and form deflection. Running out of concrete before the job is finished is a major problem, so having a buffer is critical. Our calculator does not include this overage, so you should add it to the final volume.

A 4-inch thickness is standard for most residential projects like patios, sidewalks, and shed foundations. For driveways or slabs that will support heavier loads like large vehicles, a thickness of 5 to 6 inches is recommended for added strength and durability.

While this calculator doesn't account for reinforcement, it is highly recommended for most slabs. Rebar or wire mesh adds tensile strength, helping to control cracking and increase the overall durability of the concrete. The specific type and spacing will depend on your project and local building codes.

Pre-mixed bags are ideal for very small projects, like setting a fence post or a small pad for an AC unit. For anything larger than a few cubic feet, mixing bags becomes very labor-intensive. If your project requires 1 cubic yard or more, ordering ready-mix concrete from a truck is almost always more efficient and cost-effective.