How to Calculate Concrete Volume

Concrete is sold by the cubic yard, so you need to calculate the volume of your project area. Converting from cubic feet to cubic yards requires dividing by 27.

The Formula

Cubic Yards = (L x W x D) / 27

Where:

LLength — Length of the area in feet
WWidth — Width of the area in feet
DDepth — Thickness of the slab in feet

Step-by-Step Example

Here's how to calculate concrete volume step by step:

  1. 1Measure dimensions: Measure length, width, and desired depth in feet.
  2. 2Calculate cubic feet: Multiply length x width x depth for total cubic feet.
  3. 3Convert to cubic yards: Divide cubic feet by 27 to get cubic yards.
  4. 4Add 10% extra: Order 10% more to account for spillage and uneven ground.

Following these 4 steps gives you the final concrete volume value.

Skip the Math

A 20x10 ft patio that is 4 inches deep needs (20x10x0.333)/27 = 2.47 cubic yards, so order about 2.75 yards.

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Why You Need This Calculation

  • Accurate concrete estimation prevents costly over-ordering or project-stopping shortages on pour day.

Common Mistakes

Forgetting to convert inches to feet for depth.

Divide inches by 12 to get feet (4 in = 0.333 ft).

Not adding waste allowance.

Always add 5-10% extra for spillage and uneven surfaces.

Using square feet instead of cubic feet.

You must include the depth dimension for volume.

Frequently Asked Questions