Concrete Calculator

Volume = length x width x thickness (all in feet), divided by 27 to convert cubic feet to cubic yards. For example, a 10 x 10 foot slab, 4 inches (0.333 feet) thick: 10 x 10 x 0.333 / 27 = 1.23 cubic yards. Always add 10% for waste.

A 60-lb bag of concrete yields approximately 0.45 cubic feet. An 80-lb bag yields approximately 0.60 cubic feet. Convert your volume to cubic feet (multiply cubic yards by 27), then divide by the yield per bag. For example, 1.23 cubic yards = 33.2 cubic feet. At 0.60 cubic feet per 80-lb bag: 33.2 / 0.60 = 56 bags.

Ready-mix concrete from a truck is more cost-effective for large pours (typically 1 cubic yard or more). Pre-mixed bags are more practical for small jobs. Ready-mix is typically charged per cubic yard with a minimum delivery (usually 1 yard), plus delivery fees.

Residential driveways should be at least 4 inches thick, and 5-6 inches for heavy vehicles. Patios and sidewalks typically use 3-4 inches. Footings for structures must meet local building code requirements, which often require the footing to be at least as deep as its width and below the frost line.

Concrete strength is measured in PSI (pounds per square inch). Standard residential concrete mixes are 3,000-4,000 PSI. Higher strength mixes (4,000-5,000 PSI) are used for driveways and high-traffic areas. Structural applications like footings and foundations often require 4,000+ PSI. Strength is achieved through the water-to-cement ratio and curing time.