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Construction

Verified calculator with a transparent formula

Construction

Concrete Yardage Calculator.

Estimates the volume of concrete needed for a slab in cubic yards based on length, width, and thickness.

Results update live as you type.
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Your inputs

How it works

  1. 1

    Convert thickness from inches to feet by dividing by 12.

  2. 2

    Multiply length, width, and thickness in feet to get cubic feet.

  3. 3

    Divide cubic feet by 27 to convert to cubic yards.

  4. 4

    Round the result to two decimal places.

round((length * width * (thickness / 12)) / 27 * 100) / 100

Frequently asked questions

How do I account for waste or overage?

Add 5-10% to the calculated yardage to cover spillage, uneven subgrade, or slight over-excavation.

Can I use this for round or irregular shapes?

No, this calculator is for rectangular slabs. For other shapes, break them into rectangles or use a different method.

What if my thickness is in inches but I want feet?

The calculator handles the conversion automatically. Just enter the thickness in inches.

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Results

Formula checked

Concrete Needed

1.23cu yd

Ask Anything

Estimate for general guidance only — verify important decisions with an appropriate professional.

How it works

Estimates the volume of concrete needed for a slab in cubic yards based on length, width, and thickness.

  1. Convert thickness from inches to feet by dividing by 12.
  2. Multiply length, width, and thickness in feet to get cubic feet.
  3. Divide cubic feet by 27 to convert to cubic yards.
  4. Round the result to two decimal places.

Formulas

The math behind this calculator, written out so you can verify the result.

Volume of a rectangular slab

V = L × W × T

Multiply length, width, and thickness (all in feet) to get volume in cubic feet.

Example:

Input: L=10 ft, W=10 ft, T=4 in (0.333 ft)

Calculation: 10 × 10 × 0.333 = 33.3 cu ft

Result: 33.3 cu ft = 1.23 cu yd

Real-world use cases

Where this calculation shows up in everyday life.

Patio or walkway

Plan concrete for a new patio or walkway by entering the dimensions.

Example: 10 ft × 12 ft × 4 in

Footings or foundations

Estimate concrete for footings or foundation slabs.

Example: 20 ft × 20 ft × 8 in

Driveway or garage floor

Calculate the concrete needed for a driveway or garage floor.

Example: 24 ft × 24 ft × 6 in

Tips and common mistakes

Tips

  • Always order a little extra concrete (5-10%) to avoid running short.
  • Check with your supplier for minimum order quantities.
  • Use a laser level to ensure the subgrade is even before pouring.
  • Consider using rebar or wire mesh for added strength.

Common Mistakes to Avoid

  • Forgetting to convert thickness from inches to feet.
  • Not accounting for waste or over-excavation.
  • Mixing up cubic feet and cubic yards (1 cu yd = 27 cu ft).

Assumptions and limitations

  • Use the stated inputs and units.
  • Results are estimates for planning and education.
  • Check measurements and source data before making an important decision.