Find out how many cubic yards of concrete you need for a slab, footing or driveway. Enter your dimensions below and get cubic yards, cubic meters and bag count instantly.
One cubic yard = 27 cubic feet. One 80 lb bag yields about 0.022 cubic yards (about 45 bags per yard).
Concrete is sold by the cubic yard, so you need to convert your slab's volume into yards before you order. The formula is simple:
Length (ft) × Width (ft) × Thickness (ft) ÷ 27 = Cubic Yards
Since thickness is usually measured in inches, convert it to feet first by dividing by 12. A 4-inch slab is 4 ÷ 12 = 0.333 feet thick. For a 10 × 4 foot slab at 4 inches thick, that works out to 10 × 4 × 0.333 ÷ 27 = 0.49 cubic yards.
Always order about 10% extra to cover uneven ground, form spillage and slight over-digging. Running out of concrete in the middle of a pour means a cold joint and a weak slab, so a small overage is cheap insurance.