gizmo421

Concrete Calculator

Planning a slab, footing, or tube form? Enter your dimensions and this calculator tells you how many cubic yards (or bags) of concrete the job needs — so you don’t end up short mid-pour or paying for a whole extra truck you don’t need.

Slabs, square footings, or walls

Holes, columns, or round footings

Circular slabs or tubes

Three ways to measure concrete

Concrete is ordered by the cubic yard (one yard is 27 cubic feet), and every shape gets measured the same way: area times depth. The calculator handles the three most common jobs — slabs (length × width × thickness), footings and holes (round shafts, like for deck posts or fence columns), and tubes (cylindrical forms such as Sonotubes).

Pro tips before you order

  • Round up, don’t round down. Order 5–10% more than the math says. Odd shapes, uneven subgrade, and spillage eat into a perfect estimate fast — a short pour is a disaster, a leftover half-yard is not.
  • Thickness matters more than area. Going from a 4-inch slab to 6 inches is a 50% increase in concrete. Make sure the thickness you enter is the real, finished depth.
  • Check the bag math. For small jobs, the calculator converts cubic yards to 80-lb bags of premix so you can compare a bagged pour against ready-mix delivery.
  • Mind the weather. Ready-mix starts a clock when it leaves the plant; schedule your pour for a day you can work fast.

    • Why trust the math?

    This calculator is built in-house from the plain volume formulas — length × width × depth for slabs, π × (diameter ÷ 2)² × depth for round footings, and π × (outer radius² − inner radius²) × length for tubes — using the standard 133 lbs-per-cubic-foot density of mixed concrete. Everything runs entirely in your browser: your measurements never leave your device.