Concrete for a 12×12 Slab at 4 Inches Thick

Quick answer

A 12 × 12 ft slab at 4 inches thick has 48 cubic feet of volume, which is about 1.78 cubic yards before adding waste.

Formula or method

Step-by-step

1. Convert 4 inches to feet: 4 ÷ 12 = 0.3333 ft.
2. Multiply 12 × 12 × 0.3333 = 48 ft³.
3. Divide 48 by 27 to get 1.78 yd³.
4. Add the project-specific waste allowance if appropriate.

Worked example

With a 10% waste allowance, 1.7778 × 1.10 = about 1.96 cubic yards.

How to interpret the result

This assumes a rectangular slab with uniform 4-inch thickness. Thickened edges, footings or uneven grade require additional volume.

Common mistakes

• Using 4 feet instead of 4 inches.
• Forgetting to divide cubic feet by 27 for cubic yards.
• Assuming the whole slab is exactly the design thickness.