How concrete volume is calculated
Multiply your length by width by thickness to find cubic feet. Since thickness is often measured in inches, convert it to feet first by dividing by 12. There are 27 cubic feet in one cubic yard.
A 10-foot by 10-foot slab at 4 inches deep is 33.3 cubic feet, or about 1.23 cubic yards. This calculator also converts that volume to an approximate number of 80-pound bags for smaller jobs.
Do not order exactly the calculated amount for a delivery. Many projects need a waste allowance, and local suppliers may have a minimum order.
Common slab thicknesses
A 4-inch slab is common for patios and walkways, while loads, local frost conditions, reinforcement, and soil can require a different design. The dimensions in this calculator are an estimate, not an engineering plan.