Slab & rectangular volume

How it is calculated

V = length × width × (thickness in inches / 12) × count; yd³ = ft³ / 27.

Keep the full result when using it in another calculation. Results show up to three decimal places; very small positive results use scientific notation (for example, 1e-6). No extra material for waste is added.

Measure the dimensions of the space being filled

Measure the clear length and width of the concrete space. For a formed slab, measure between the inside faces of the forms. Measure thickness perpendicular to the flat surface. This calculator accepts thickness in inches while length and width are in feet.

For an L-shaped or otherwise irregular footprint, divide the plan into nonoverlapping rectangles. Calculate each rectangle separately and add the volumes. Do not include the same corner or section in two rectangles.

Read both volume units

A 12 ft by 10 ft slab that is 4 in thick contains 40 ft³ of concrete: 12 × 10 × (4 ÷ 12). The same volume is about 1.481 yd³ because one cubic yard equals 27 cubic feet.

Use whichever unit matches the next estimate or supplier quote. The displayed volume describes the measured shape; it does not include a waste allowance or convert the volume to bags without a product yield.

Before you use the result

• The footprint must be rectangular and the thickness must be the same throughout. Measure thickness at a right angle to the slab or wall surface.
• If you enter more than one component, each must have the same dimensions. Do not count overlapping concrete twice. No extra material for waste is added.

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