Landscape suppliers sell gravel, soil, sand and mulch by the cubic yard, but your plan is measured in feet and inches. Convert wrongly and you either pay for a half-empty truck or you stand in a half-finished driveway waiting for a second delivery. The maths is short once you see it, and this guide walks through every case.
- What a cubic yard actually is
- The core formula
- Depth: the unit that trips people up
- Rectangles, circles, triangles and irregular areas
- Coverage chart: square feet per cubic yard
- Worked example: a gravel driveway
- Compaction, settling and waste
- Converting volume to weight (tons)
- Typical depths by material
- Mistakes that cost money
- FAQ
- References
What a cubic yard actually is
A cubic yard is the volume of a cube measuring 3 feet by 3 feet by 3 feet. Multiply it out and you get 27 cubic feet, which is the single most useful number in the whole job. Everything below is a way of getting your area into cubic feet and then dividing by 27.
In metric terms, one cubic yard is about 0.7646 cubic metres, so a cubic metre is about 1.31 cubic yards. If your supplier uses metric, convert at the end rather than midway to avoid rounding errors.
The core formula
Cubic yards = length (ft) x width (ft) x depth (ft) / 27
All three measurements must be in feet before you multiply. That is where most mistakes begin, because depth is almost always given in inches.
Skip the arithmeticEnter length, width and depth in any unit and get cubic yards, with an allowance for waste.
Open the Cubic Yard CalculatorDepth: the unit that trips people up
To turn inches into feet, divide by 12. Memorise a few common depths so you can work quickly:
| Depth in inches | Depth in feet |
|---|---|
| 1 in | 0.0833 |
| 2 in | 0.1667 |
| 3 in | 0.25 |
| 4 in | 0.3333 |
| 6 in | 0.5 |
| 8 in | 0.6667 |
| 12 in | 1.0 |
The classic error is typing 3 for a 3 inch depth, which makes the answer twelve times too big. If your result seems absurdly large, check the depth first.
Rectangles, circles, triangles and irregular areas
Rectangle or square: area = length x width.
Circle: area = 3.1416 x radius x radius. The radius is half the diameter. A round bed 10 feet across has a radius of 5 and an area of 3.1416 x 25 = 78.5 square feet.
Triangle: area = base x height / 2.
Irregular shapes: split the space into rectangles, circles and triangles, calculate each one, and add them together. For a curved border, an average width times the length is accurate enough. If you work in square feet often, the Square Footage Calculator handles combined shapes and avoids slips.
Once you have the total area in square feet, the rest is one step: multiply by depth in feet and divide by 27.
Coverage chart: square feet per cubic yard
This is the table professionals keep in their heads. One cubic yard (27 cubic feet) covers this much area at each depth:
| Depth | Area covered by 1 cubic yard | How it is calculated |
|---|---|---|
| 1 in | 324 sq ft | 27 / 0.0833 |
| 2 in | 162 sq ft | 27 / 0.1667 |
| 3 in | 108 sq ft | 27 / 0.25 |
| 4 in | 81 sq ft | 27 / 0.3333 |
| 6 in | 54 sq ft | 27 / 0.5 |
| 12 in | 27 sq ft | 27 / 1 |
The shortcut is 324 divided by the depth in inches. For a 3 inch mulch layer, 324 / 3 = 108 square feet per yard. A 540 square foot garden needs 540 / 108 = 5 cubic yards.
Worked example: a gravel driveway
You want a driveway 40 feet long and 10 feet wide, with 4 inches of gravel.
- Depth in feet: 4 / 12 = 0.3333.
- Volume in cubic feet: 40 x 10 x 0.3333 = 133.33.
- Cubic yards: 133.33 / 27 = 4.94.
- Add 10 percent for compaction and uneven ground: 4.94 x 1.10 = 5.43 cubic yards.
- Order 5.5 cubic yards, or round up to 6 if your supplier sells in half or whole yards.
Check with the coverage chart: at 4 inches, one yard covers 81 square feet. The driveway is 400 square feet, and 400 / 81 = 4.94. The two methods agree.
Compaction, settling and waste
The number from the formula is the volume of finished material. Loose material settles, so you order more than you calculate. A reasonable allowance:
- Gravel and crushed stone: 10 to 15 percent extra, because it compacts under a plate compactor or vehicles.
- Topsoil and fill: 10 to 20 percent, since soil settles after watering and rain.
- Mulch and bark: 5 to 10 percent, as it decomposes and thins at edges over time.
- Sand for paving bases: about 10 percent.
These are common planning allowances, not guarantees. Uneven subgrade, soft ground and tricky edges can push the number higher. If a job has hard-to-measure depth, measure it at several points and use the average.
Converting volume to weight (tons)
Some quarries sell by the ton instead of by the cubic yard. Weight depends on the material and how wet it is, so always confirm with your supplier. Common planning figures for loose material are:
| Material | Approximate tons per cubic yard |
|---|---|
| Crushed stone or gravel | 1.2 to 1.5 |
| Sand (dry to damp) | 1.3 to 1.5 |
| Topsoil | 1.0 to 1.3 |
| Mulch (bark or wood) | 0.3 to 0.5 |
| Concrete (wet) | about 2 (4,000 lb) |
For the driveway example, 5.43 yards of gravel at about 1.4 tons per yard is roughly 7.6 tons. Wet material is heavier, so ask whether the quote is for tons or yards and what moisture the weight assumes.
Typical depths by material
- Mulch: 2 to 3 inches in beds. Thicker layers can suffocate roots and hold too much moisture.
- Topsoil for a lawn: 4 to 6 inches for a new lawn, 1 to 2 inches when top-dressing.
- Gravel driveway: 4 to 6 inches over a compacted base, thicker for heavy vehicles.
- Paver base: 4 to 6 inches of compacted aggregate, plus about 1 inch of bedding sand.
- Garden path: 2 to 3 inches of gravel over landscape fabric.
- Raised bed fill: fill to the full depth of the bed, then top up each year as it settles.
For hard surfaces, the same volume thinking applies to concrete. Our guide on calculating concrete for a slab covers pours in detail, and the Mortar Calculator and Retaining Wall Block Calculator cover related materials.
Mistakes that cost money
- Mixing units. Feet times inches gives nonsense. Convert first.
- Forgetting to divide by 27. You end up with cubic feet and order 27 times too much.
- Skipping the allowance. The exact figure is the minimum, not the order quantity.
- Measuring the plan, not the ground. Slopes and dips use more material. Measure real depth on site.
- Ignoring delivery minimums. Many suppliers have a minimum load or a delivery fee. Ordering 1 yard may cost nearly as much as 3.
- Confusing yards and tons. A quote for 5 tons is not 5 yards. Convert with the density in the table.
- Forgetting the base layers. A paved path may need stone, sand and pavers, each a separate calculation.
Frequently asked questions
How many square feet does one cubic yard cover?
It depends on depth. Divide 324 by the depth in inches: 108 square feet at 3 inches, 81 at 4 inches, 54 at 6 inches.
How many cubic feet are in a cubic yard?
27, because 3 x 3 x 3 = 27.
How much mulch do I need for 500 square feet at 3 inches?
500 / 108 = 4.63 cubic yards. Round up to 5 yards, allowing a small extra for thin patches.
Is a bag of mulch the same as a cubic yard?
No. Bags are commonly 2 or 3 cubic feet, so you need about 13 bags of 2 cubic feet, or 9 bags of 3 cubic feet, to equal one yard (27 divided by the bag size).
How do I calculate a round bed?
Find the area with 3.1416 x radius squared, multiply by depth in feet, then divide by 27.
Do I round up or down?
Up. A small surplus is easy to use elsewhere; a shortfall means a second delivery charge and a visible seam in the finished layer.
Related guides and tools
References
- NIST, “Unit conversion”: cubic yard to cubic metre. nist.gov
- Wikipedia, “Cubic yard”. en.wikipedia.org
Densities and allowances are typical planning figures. Always confirm weight, moisture and minimum order with your supplier before you buy, and have a professional assess structural or drainage work.