Concrete Slab Calculator (Full Material Package)

A slab is more than concrete. This calculator gives you the complete material package for a slab on grade: concrete volume, wire mesh and vapor barrier areas with overlap, and the loose base rock needed to reach your compacted base depth.

Slab-on-Grade Package

Length

Width

Slab Thickness

Base Rock Depth

Waste / Overage

Enter your slab dimensions to see the full material package: concrete, mesh, vapor barrier, and base rock.

What’s included

Enter your slab dimensions once and get four quantities: concrete (with your waste percentage), wire mesh sized at 10% over the slab area for overlaps, vapor barrier at the same overlap allowance, and base rock converted from compacted depth to the loose volume you actually order, at a 15% compaction allowance and a typical 1.5 tons/yd³ density.

Why the base rock number is bigger than you expect

Base rock compacts as it’s plate-tamped or rolled. To end up with a 4-inch compacted base you need to spread more than 4 inches of loose material, which is why the calculator adds a compaction allowance on top of the geometric volume.

Frequently Asked Questions

What goes under a concrete slab?

A typical residential slab sits on compacted base rock (commonly 4 inches), with a polyethylene vapor barrier between the base and the concrete, and wire mesh or rebar within the slab for crack control.

How much overlap do wire mesh and vapor barrier need?

Sheets are overlapped at seams — commonly around 6 inches for vapor barrier and one full square for mesh. The calculator sizes both at 10% over the slab area to cover overlaps and edge trim.

How thick should a concrete slab be?

Four inches is standard for patios, walkways, and shed slabs. Driveways and garage slabs are typically 5–6 inches. Heavier loads need engineering judgment.