Formula when all three dimensions are in feet
For a rectangle or box, multiply length × width × height to get cubic feet. Divide by 27 to convert cubic feet to cubic yards. Example: a 9 × 6 × 1.5 ft volume is 81 cubic feet or exactly 3 cubic yards.
Always use the same linear units before multiplying. Mixing feet and inches without a conversion is a common source of errors.
Formula when depth is in inches
Most landscape projects measure length and width in feet but thickness in inches. The shortcut is length × width × depth ÷ 324. For a 12 × 10 ft garden bed that is 3 inches deep, the volume is about 1.11 cubic yards.
Formula using square footage
If you already know the area in square feet, multiply that area by depth in inches and divide by 324. For 200 square feet at 4 inches, the result is about 2.47 cubic yards.
Circular and irregular shapes
A circular footprint has area π × radius². Multiply that area by depth in compatible units, then convert to cubic yards. For irregular projects, divide the area into smaller shapes and add their individual volumes.
From calculated volume to material order
The geometric volume is only one part of purchasing. Concrete may require allowances for construction conditions; soil and aggregate can be delivered loose and compacted after placement. Verify units, material type and supplier billing method.
Frequently Asked Questions
Why divide by 27?
A cubic yard is 3 feet × 3 feet × 3 feet, which equals 27 cubic feet.
Why divide by 324 for depth in inches?
There are 12 inches in a foot and 27 cubic feet in a cubic yard, so the divisor is 12 × 27 = 324.
Related Calculators and Guides
Continue with a material-specific estimate, convert units, or review the calculation behind your result.