Concrete Calculator

Concrete volume is a box: length × width × thickness. The only thing that trips people up is units. This calculator takes length and width in feet and thickness in inches, converts everything to cubic feet, then divides by 27, because a cubic yard is 27 cubic feet.

Formula: volume (ft³) = length × width × (thickness ÷ 12). Cubic yards = volume ÷ 27.

Bag counts come from dividing that volume by what a single bag yields, about 0.45 ft³ for a 60 lb bag and 0.6 ft³ for an 80-pound bag, per the standard manufacturer spec sheets. We round up, since you can't buy a partial bag.

Pouring something structural that needs reinforcement? Run the same length and width through the Rebar Calculator to get grid spacing and total linear footage.

This calculator sizes the order. It doesn't price it, and it doesn't pick the mix: 3,000 psi is the usual residential baseline, and driveways or garage floors often step up to 4,000 psi, which moves the price more than the volume. For dollars, put the same dimensions into the Concrete Cost Calculator, or the Driveway Cost Calculator if you're still deciding between concrete, asphalt, and gravel.

Hauling it yourself, or pouring onto something that has to carry it? See how much a yard of concrete weighs before you commit to a trailer.

Pouring a round pad or a triangular corner? The Cubic Yard Calculator works out cubic yards for circles and triangles too.

For a block wall instead of a poured one, the Concrete Block Calculator counts blocks, mortar and grout. The current concrete price per yard turns these cubic yards into a material cost, and the Retaining Wall Calculator covers segmental wall block.