Concrete Calculator

Length (ft). Measure the full length of the slab or straight footing along its long direction. Use the actual placement dimensions from the forms or plans, rather than the length of a nearby wall that may have different end conditions.

Width (ft). Measure across the slab or footing, perpendicular to its length. Use the width of concrete being placed. A footing that widens at a column or changes size along its length should be divided into separate calculations.

Thickness (in). For a slab, measure the concrete thickness from the bottom of the placement to its finished top. In footing mode this field is the footing’s vertical depth. Enter inches here; it is not the depth of the excavation below grade unless those dimensions happen to be the same.

Diameter (in). For a round pier, measure all the way across the circular concrete section through its center. This is the diameter, not the radius. Use the inside diameter of the form or the intended concrete diameter.

Depth (ft). Measure the vertical length of the round concrete pier, from the bottom of the placement to its finished top. Enter feet in this field. Any enlarged footing beneath the pier needs a separate volume calculation.

Extra allowance (%). Enter the percentage you want to add for cutting, handling loss or other conditions specific to this work. Apply it to the measured quantity rather than enlarging the measurements as well. The suggested value is editable, not a universal recommendation; enter zero when no allowance is needed.

Concrete shape. Choose the shape that matches the concrete placement: a rectangular slab, a straight rectangular footing, or a round pier. Calculate separate shapes or changes in cross-section separately and combine their volumes when planning the order.

Net volume describes the concrete before the extra allowance, in both cubic feet and cubic yards. Estimated volume includes the entered allowance and is the quantity to discuss with the supplier. It is not automatically rounded to a supplier’s ordering increment, and it does not establish appropriate footing dimensions or reinforcement.

Slab or rectangular footing: cubic feet = length (ft) × width (ft) × thickness or depth (in) ÷ 12.
Round pier: radius (ft) = diameter (in) ÷ 24; cubic feet = π × radius² × depth (ft).
Cubic yards = cubic feet ÷ 27.
Estimated cubic yards = net cubic yards × (1 + allowance percentage ÷ 100).

Slab example: 10 ft × 10 ft × 4 in = 33.3333 cubic feet, or 1.2346 cubic yards net. Adding 10% gives 1.3580 cubic yards . Footing example: 40 ft × 2 ft × 12 in = 80 cubic feet, or 2.9630 cubic yards net. Pier example: A 12-inch diameter gives a 0.5-foot radius. At 4 ft deep, π × 0.5² × 4 = 3.1416 cubic feet, or 0.1164 cubic yards net.

Volume only, not structural design. This tool does not determine suitable footing dimensions, reinforcement, or structural adequacy. Final order quantities depend on site conditions, over-excavation, supplier minimums, and other factors.