How to Use

1
Select imperial (feet/inches) or metric (meters/centimeters)
2
Enter the length and width of the slab, then the depth (thickness)
3
Click Calculate to get cubic yards or meters, plus equivalent 60-lb and 80-lb bag counts

Formula

Volume (cu ft) = Length (ft) × Width (ft) × Depth (ft)

Cubic Yards = Volume (cu ft) ÷ 27

Depth in inches is divided by 12 to convert to feet before the multiplication. 60-lb bags yield approximately 0.45 cu ft each; 80-lb bags yield approximately 0.60 cu ft each.

Examples

10 × 10 ft patio slab, 4 inches deep

10 × 10 × (4/12) = 33.33 cu ft ÷ 27 = 1.23 cubic yards

Result: 1.23 cu yd - ~56 bags (60-lb) or ~41 bags (80-lb)

Garden walkway: 20 × 3 ft, 4 inches deep

20 × 3 × (4/12) = 20 cu ft ÷ 27 = 0.74 cubic yards

Result: 0.74 cu yd - ~34 bags (60-lb) or ~25 bags (80-lb)

Driveway apron: 12 × 8 ft, 6 inches deep

12 × 8 × (6/12) = 48 cu ft ÷ 27 = 1.78 cubic yards

Result: 1.78 cu yd - ~80 bags (60-lb) or ~59 bags (80-lb)

FAQ

Most residential patios and walkways are 4 inches thick - sufficient for foot traffic. Driveways should be 5-6 inches to support vehicle weight. Areas with heavy frost may require deeper footings underneath.

Pre-mixed bags are practical for projects under 1 cubic yard, or about 50 or fewer 60-lb bags. For anything larger, ordering ready-mix concrete by the yard from a local plant is more cost-effective and less labor-intensive.

For light-duty patios and walkways, wire mesh (6×6 in, W1.4×W1.4) is sufficient. Driveways and areas supporting heavy loads benefit from #3 or #4 rebar on a 12-18 inch grid. Consult local building codes for specific requirements.