What Is a Cubic Yard?

A cubic yard is a unit of volume. It is the space inside a cube that measures 1 yard (3 feet) on every side. Bulk landscape materials such as mulch, topsoil, and gravel, and ready-mixed concrete, are commonly sold by the cubic yard. To order the right amount, you convert your project's length, width, and depth into this unit.

How big is a cubic yard?

One yard is 3 feet. A cube that is 3 ft long, 3 ft wide, and 3 ft tall holds 3 × 3 × 3 = 27 cubic feet. NIST Handbook 44 states the same definition: 27 cubic feet = 1 cubic yard.

1 yd³ = 3 ft × 3 ft × 3 ft = 27 ft³
1 ft³ = 1/27 yd³ ≈ 0.037 yd³

A common mistake is to treat a cubic yard as 3 cubic feet, or a square yard as 3 square feet. Neither is right. A square yard is 3 × 3 = 9 ft², and a cubic yard is 27 ft³. Dividing by 3 instead of 27 overstates the order nine times.

Converting area × depth to cubic yards

Every flat, even-depth job follows the same three steps:

1. Find the area in square feet. For a rectangle, that is length × width. For other shapes, see measuring irregular areas.
2. Convert the depth to feet. Depth is usually given in inches, so divide by 12.
3. Multiply area × depth to get cubic feet, then divide by 27 to get cubic yards.

cubic feet  = length (ft) × width (ft) × depth (in) ÷ 12
cubic yards = cubic feet ÷ 27
            = area (ft²) × depth (in) ÷ 324

The shortcut at the bottom combines both divisions: 12 × 27 = 324. Keep every length in the same unit before you multiply. Mixing feet and inches in one product is the most common source of a wrong answer.

How much area does one cubic yard cover?

Rearranging the shortcut gives the area one cubic yard covers at a given depth: 324 ÷ depth in inches. The table below is pure geometry. It assumes an even layer and no settling, so treat it as a starting point.

Doubling the depth halves the coverage. A yard that covers 162 ft² at 2 in covers only 81 ft² at 4 in.

Worked examples

Example 1: a mulch bed

A bed is 20 ft long and 10 ft wide, and you want 3 in of mulch.

Area        = 20 ft × 10 ft = 200 ft²
Depth       = 3 in ÷ 12 = 0.25 ft
Volume      = 200 ft² × 0.25 ft = 50 ft³
Cubic yards = 50 ÷ 27 = 1.852 yd³

The bed needs about 1.85 cubic yards. You can check the result with the mulch calculator.

Example 2: a gravel path

A path is 40 ft long and 4 ft wide, with 4 in of gravel.

Area        = 40 ft × 4 ft = 160 ft²
Shortcut    = 160 ft² × 4 in ÷ 324 = 1.975 yd³
Check       = 160 × 4 ÷ 12 = 53.33 ft³; 53.33 ÷ 27 = 1.975 yd³

The path needs just under 2 cubic yards before any allowance. The gravel calculator adds an allowance and rounds to supplier steps.

Example 3: how far will a fixed amount go?

You have 2 cubic yards of topsoil and want a 3 in layer. How much ground will it cover?

Area = yards × 324 ÷ depth (in)
     = 2 × 324 ÷ 3 = 216 ft²

Metric equivalents

The foot is defined as exactly 0.3048 meters, and NIST lists that factor as exact. A cubic yard is 27 ft³, and each cubic foot is 0.3048³ m³, so the conversion is also exact:

1 yd³ = (3 × 0.3048 m)³ = 0.9144³ m³
      = 0.764554857984 m³ (exact)
1 m³  = 1 ÷ 0.764554857984 ≈ 1.308 yd³

For quick estimates, one cubic meter is a little over 1.3 cubic yards. Use the full factor when you convert an actual order, because the small difference adds up on larger jobs.

Example 4: a metric job converted to yards

A 5 m × 3 m area needs a 10 cm layer, but the supplier sells in cubic yards.

Volume      = 5 m × 3 m × 0.1 m = 1.5 m³
Cubic yards = 1.5 ÷ 0.764555 = 1.962 yd³

Loose volume vs. placed volume

The arithmetic above gives the geometric volume of the space you want to fill. What arrives on the truck may not fill exactly that space once it is spread. Several things change the result:

• Settling and compaction. Loose materials such as gravel, soil, and mulch can settle after they are spread, raked, watered, or compacted. A layer that measures 3 in on day one may be thinner later.
• How the supplier measures. Some materials are measured loose in a bucket or bin. Others are sold by weight and converted. Ask your supplier how they measure a yard of that material.
• Uneven ground. Low spots and ruts take extra material that a flat-area formula does not count.

How much a given material settles depends on the material, its moisture, and how it is placed. This site does not publish a single compaction percentage, because no one figure applies to every product. If your supplier or project specification gives a factor for your material, apply it. Otherwise, add a planning allowance that matches your confidence in the measurements, and see planning a material delivery for how to turn the result into an order.

Quick checks before you order

• Did you divide depth in inches by 12, and cubic feet by 27 (not 3 or 9)?
• Are all lengths in the same unit before multiplying?
• Does the answer pass a sanity check against the coverage table above?
• If you are buying bags instead of bulk, have you converted using the bag volume printed on the package? See bagged vs. bulk materials.