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Concrete Cubic Yards illustration

Construction · Quantity

Concrete Cubic Yards

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Use this to estimate how many cubic yards of concrete a rectangular slab needs from its dimensions in feet.

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Interactive workbench

Patio slab

Length×Width×Thickness27

A 20x10 ft slab at 0.33 ft thick needs about 2.44 cubic yards.

Step 1 of 4

Variables and units

  • Length (ft)

    Slab length in feet.

    count

  • Width (ft)

    Slab width in feet.

    count

  • Thickness (ft)

    Slab thickness in feet (e.g. 0.33 for 4 inches).

    count

Common mistakes

  • Entering thickness in inches instead of feet.
  • Forgetting a waste allowance for the pour.

Step-by-step example

Patio slab

  1. 1. Start with the example inputs

    • Length (ft)20
    • Width (ft)10
    • Thickness (ft)0.33

  2. 2. Apply the formula

    Length×Width×Thickness27

  3. 3. Run the numbers

    2.44

    A 20x10 ft slab at 0.33 ft thick needs about 2.44 cubic yards.

What this result means

The slab needs 2.44 cubic yards of concrete. Order with a small cushion — a 5–10% over-order is common, because coming up short mid-pour costs far more than the extra yardage — and check the supplier's minimum-load terms.