Quick answer: to calculate cubic yards, multiply length × width × depth with every measurement in feet, then divide by 27. A cubic yard is a cube 3 feet on each side, which is 3 × 3 × 3 = 27 cubic feet. For example, a 10 × 10 ft area filled 4 inches deep is 10 × 10 × 0.333 = 33.3 cubic feet, which is 1.23 cubic yards.
Suppliers of concrete, soil, gravel, mulch and sand quote by the cubic yard, so this one calculation covers most home projects. You can also use the Cubic Yard Calculator. The rest of this page explains each step and the shapes people get wrong.
The basic formula
Cubic feet = length (ft) × width (ft) × depth (ft)
Cubic yards = cubic feet ÷ 27
The part that trips people up is depth. Depth is almost always measured in inches, but the formula needs feet. Divide inches by 12:
| Depth | In feet |
|---|---|
| 1 in | 0.083 |
| 2 in | 0.167 |
| 3 in | 0.250 |
| 4 in | 0.333 |
| 6 in | 0.500 |
| 12 in | 1.000 |
Worked example: a rectangle
A planting bed 20 ft long and 5 ft wide, filled 6 inches deep:
- Depth in feet: 6 ÷ 12 = 0.5.
- Cubic feet: 20 × 5 × 0.5 = 50 ft³.
- Cubic yards: 50 ÷ 27 = 1.85 yd³.
Cubic yards for a 10 × 10 ft area at common depths
| Depth | Cubic feet | Cubic yards |
|---|---|---|
| 1 in | 8.3 | 0.31 |
| 2 in | 16.7 | 0.62 |
| 3 in | 25.0 | 0.93 |
| 4 in | 33.3 | 1.23 |
| 6 in | 50.0 | 1.85 |
You can scale this table. A 20 × 10 ft area is twice the 10 × 10 figures.
Other shapes
Circles and round holes
Area = π × radius² = 3.1416 × (diameter ÷ 2)²
Cubic feet = area × depth (ft)
A circular patio 12 ft across and 4 in thick: area = 3.1416 × 6² = 113.1 ft². Volume = 113.1 × 0.333 = 37.7 ft³ = 1.40 yd³.
Triangles
Area = ½ × base × height
A triangular garden bed with sides of 6 ft and 8 ft at the right angle, covered 3 inches deep, has an area of ½ × 6 × 8 = 24 ft². Volume = 24 × 0.25 = 6 ft³ = 0.22 yd³.
Cylinders and columns
A round column 3 ft in diameter and 4 ft tall has a volume of 3.1416 × 1.5² × 4 = 28.3 ft³, which is 1.05 yd³.
L-shapes and irregular areas
Split the area into rectangles, work out each one, and add the results. If the depth is the same everywhere, you can also add the areas first and multiply once. The Square Footage Calculator is helpful for the area step.
Unit conversions
- 1 cubic yard = 27 cubic feet
- 1 cubic yard = 46,656 cubic inches
- 1 cubic yard = 0.7646 cubic meters (NIST gives the exact factor 0.764554857984)
- 1 cubic meter = 1.308 cubic yards
If you only have metric measurements, convert each to meters, multiply, then use these factors. The Cubic Feet Calculator is useful when a product is sold by the cubic foot, like bagged soil or mulch.
Add an allowance
The formula gives a perfect volume. Real projects use more because ground is uneven, material settles or compacts, and edges waste a bit. A common practice is to add around 5 to 10% and round up to the next quarter or half yard, but the right allowance depends on the material. Topsoil.com suggests ordering about 10% over because soil settles, for example. Your supplier can tell you what they sell in and how much to allow.
From cubic yards to what you actually order
Volume is only one of several units you might need:
- Weight (tons). Convert using the material’s weight per cubic yard. Gravel is about 1.35 tons per yard, mulch about 0.25 to 0.4 tons. See our cubic yards to tons conversion guide.
- Bags. Divide cubic feet by the bag size on the label.
- Cost. Multiply cubic yards by the supplier’s per-yard price, including any delivery fee or minimum.
Common mistakes
- Leaving depth in inches. If you multiply 10 × 10 × 4 you get 400, which is not cubic feet. Convert 4 inches to 0.333 feet first.
- Dividing by 9 instead of 27. Nine is for converting square feet to square yards (area), not cubic feet to cubic yards (volume).
- Using diameter as radius. Halve the diameter before squaring.
- Rounding too early. Keep decimals until the final step, then round up at the end.
- Forgetting multiple identical items. Eight deck footings of the same size is eight times one footing.
Quick checks
Two sanity checks catch most errors:
- Rule of 100. One cubic yard spread 1 inch deep covers about 324 square feet. At 3 inches it covers 108. If your answer looks far from that, recheck the units.
- Sizing against a known object. A cubic yard is roughly the size of a washing machine, according to North Bay Materials. If your result for a small bed is several yards, something is off.
Frequently asked questions
How many cubic feet are in a cubic yard?
27.
How many cubic yards are in 100 square feet at 4 inches?
100 × 0.333 = 33.3 ft³ ÷ 27 = 1.23 cubic yards.
How do I convert cubic feet to cubic yards?
Divide by 27. 54 cubic feet is 2 cubic yards.
How do I convert cubic yards to square feet of coverage?
Divide 27 by the depth in feet. At 3 inches (0.25 ft) one yard covers 27 ÷ 0.25 = 108 ft².
How many cubic yards is a truckload?
It depends on the truck. Ask your supplier for the capacity and the material’s weight per yard so you do not overload it.
Sources
- NIST, >Guide to the SI, Appendix B.8: Factors for units listed alphabetically: exact foot, inch and cubic yard conversion factors.
- North Bay Materials, >Landscape Materials Density Chart: definition of a cubic yard and approximate coverage per yard.
- Topsoil.com, >How much does a cubic yard of topsoil weigh?: coverage per cubic yard and the ordering allowance for settling.