How to calculate cubic yards
By Dexaloop · Updated 27 October 2026 · Checked against the sources listed below
Cubic yards are cubic feet divided by 27: convert the length, width and depth to feet, multiply them, then divide by 27. A patio 12 ft by 14 ft poured 4 inches thick is 12 x 14 x 4/12 = 56 cubic feet, which is 56 / 27 = 2.07 cubic yards. The number 27 comes from the shape of a cubic yard itself: a cube 3 feet long, 3 feet wide and 3 feet high holds 3 x 3 x 3 = 27 cubic feet. This guide shows the method for slabs, beds and round holes, a shortcut for depths in inches, and how to convert to cubic meters.
Why depth causes most of the trouble
Length and width are usually measured in feet, but depth is almost always given in inches: a 4 inch slab, 6 inches of topsoil, 3 inches of base. Multiplying 12 x 14 x 4 gives 672, which is not cubic feet of anything. You must turn the inches into feet first by dividing by 12. Four inches is 4/12 ft (0.333... ft), so the right sum is 12 x 14 x 4/12.
| Depth | In feet | Square feet one cubic yard covers |
|---|---|---|
| 2 in | 0.167 | 162 |
| 3 in | 0.25 | 108 |
| 4 in | 0.333 | 81 |
| 6 in | 0.5 | 54 |
| 8 in | 0.667 | 40.5 |
| 12 in | 1 | 27 |
The third column comes from one shortcut. A cubic yard is 27 cubic feet, and a foot is 12 inches, so a cubic yard spread 1 inch thick covers 27 x 12 = 324 square feet. Divide 324 by your depth in inches to see how far one yard goes. Turned around, it gives a quick formula:
Cubic yards = square feet x depth in inches / 324
Worked example: a concrete patio
A patio is 12 ft by 14 ft and will be 4 inches thick.
- Area: 12 x 14 = 168 square feet.
- Depth in feet: 4/12 ft (0.333...). Keep it as the fraction.
- Volume: 168 x 4/12 = 56 cubic feet.
- Cubic yards: 56 / 27 = 2.07 cubic yards.
Check with the shortcut: 168 x 4 / 324 = 2.07. Same answer.
Ready-mix suppliers often deliver in set steps, such as quarter or half yards, and a short load is costly to fix mid-pour. Give the supplier your measured volume, tell them the job, and ask what to order.
Worked example: soil for a raised bed
Two raised beds are each 8 ft long, 4 ft wide and will be filled 11 inches deep.
- Area of one bed: 8 x 4 = 32 square feet. Two beds: 64 square feet.
- Volume: 64 x 11 / 12 = 58.67 cubic feet.
- Cubic yards: 58.67 / 27 = 2.17 cubic yards.
If you are buying bags instead, divide cubic feet by the volume printed on the bag. With bags marked 1.5 cubic feet, 58.67 / 1.5 = 39.1, so you would buy 40 bags. Always round bags up.
Loose soil and compost can settle after watering. Ask the supplier whether their volume is measured loose, and leave room to top up later.
Worked example: round post holes
A fence needs 8 holes, each 12 inches across and 3 ft deep, filled with concrete.
- Radius: 12 in across means a 6 in radius, which is 0.5 ft.
- Area of one hole: 3.1416 x 0.5 x 0.5 = 0.785 square feet.
- Volume of one hole: 0.785 x 3 = 2.36 cubic feet.
- Eight holes: 2.36 x 8 = 18.88 cubic feet, or 18.88 / 27 = 0.70 cubic yards.
Small volumes like this are usually bought in bags. If the post itself goes into the hole, the concrete needed is a little less, because the post takes up space.
Converting to and from metric
NIST Handbook 44 gives these relationships:
| Unit | Equals |
|---|---|
| 1 cubic yard | 27 cubic feet (exactly), about 0.765 cubic meter |
| 1 cubic meter | about 1.308 cubic yards, or 1,000 liters |
| 1 cubic foot | about 28.316 liters |
Example: a base 5 m long, 3 m wide and 10 cm deep is 5 x 3 x 0.1 = 1.5 cubic meters. Times 1.308, that is 1.96 cubic yards. If your plans are metric and your supplier sells in yards, convert once at the end rather than converting each measurement, so rounding errors do not stack up.
Odd shapes
- L-shaped slab: split it into rectangles, work out each volume, and add them.
- Depth that varies: take several depth readings across the area and use their average. If one end is 3 inches and the other 5 inches, use 4.
- Triangle: base x height / 2 gives the area; then multiply by depth as usual.
- Steps: work out each step as its own small slab and add them.
Common mistakes
- Multiplying by depth in inches. 12 x 14 x 4 = 672 is twelve times too big. Use 4/12 ft, or divide by 324 instead of 27.
- Dividing by 9. Nine turns square feet into square yards. For cubic yards it is 27.
- Using the diameter as the radius on round holes, which makes the volume four times too large.
- Rounding early. Writing 4 inches as 0.3 ft instead of 0.333 ft loses about 10% of the volume.
- Measuring the plan, not the ground. Measure the dug or formed area itself, including any low spots.
- Rounding bags down. 39.1 bags means buying 40.
Measure the area, decide the depth, then let the calculator below do the cubic feet, cubic yards and cubic meters in one go, including round holes and bag counts.
Work out cubic yards: tools.dexaloop.com/cubic-yard-calculator/. Free, no sign-up, and it runs on your device.
Questions
How do you calculate cubic yards?
Put every measurement in feet, multiply the three together for cubic feet, and divide by 27, because NIST lists one cubic yard as exactly 27 cubic feet.
How many cubic yards is a 10 x 10 slab 4 inches thick?
4 inches is 4/12 ft. 10 x 10 x 4/12 = 33.33 cubic feet, and 33.33 / 27 = 1.23 cubic yards.
How many square feet does a cubic yard cover?
Divide 324 by the depth in inches. At 4 inches one cubic yard covers 81 square feet; at 6 inches, 54 square feet; at 2 inches, 162 square feet.
How do I convert cubic meters to cubic yards?
Multiply by about 1.308. To go from cubic yards to cubic meters, multiply by about 0.765. Both figures are from NIST.
How do I work out cubic yards for a round hole or column?
Area of the circle (3.1416 x radius x radius) times the depth, all in feet, gives cubic feet. Divide by 27. A 12 inch hole 3 ft deep holds 2.36 cubic feet.
Should I order extra concrete or soil?
Real ground is rarely perfectly flat and forms can bow, so the volume you need can be more than the drawing shows. Many people add a small allowance for this. It is a common habit rather than a fixed rule, so decide your own figure and ask your supplier what they suggest for your job and whether their yards are measured loose or in place.
Sources
This guide is general information, not legal, tax or financial advice. Rules change; check the official source for your own case. Found a mistake? Email support@dexaloop.com.
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