Estimate how much ready-mix or bagged concrete you need for a slab, footing, round column or wall — with results in cubic feet, cubic yards, cubic metres and premix bag counts.
One cubic yard covers about 27 sq ft at a 12-inch thickness, or roughly 81 sq ft at a standard 4-inch slab thickness.
It takes about 45 bags of 80 lb premix concrete to make one cubic yard.
For pours over about 1 cubic yard, ready-mix delivery is usually faster and cheaper. Bagged concrete is more practical for small jobs like post holes or patch repairs.