How to Estimate Concrete

Multiply length by width to get the surface area, then multiply by the slab thickness (converted to feet) to get the volume in cubic feet. Divide by 27 to convert to cubic yards, the unit concrete is typically ordered in.

Bag Estimates

A standard 60 lb bag of concrete mix yields about 0.45 cubic feet once mixed. This calculator uses that figure to estimate how many bags a small project needs; for larger pours, ready-mix delivered by the cubic yard is usually more practical.