How to Calculate Cubic Yards

A cubic yard is a unit of volume equal to a cube that measures 3 feet on every side. It is the standard unit used to buy and sell bulk materials — concrete, mulch, gravel, topsoil, and sand are all priced and delivered by the cubic yard. If you have ever ordered a load of mulch for a garden bed or called a concrete company for a driveway pour, you were quoted a price per cubic yard.

Knowing how to calculate cubic yards yourself means you can estimate project costs accurately, avoid over-ordering expensive materials, and speak the same language as contractors and suppliers.

The Key Conversion: 1 Cubic Yard = 27 Cubic Feet

A yard is 3 feet. A cubic yard is a cube measuring 3 feet in each direction:

$1 \text{ yd}^3 = 3 \text{ ft} \times 3 \text{ ft} \times 3 \text{ ft} = 27 \text{ ft}^3$

This is the single most important number in this entire page. To convert any volume from cubic feet to cubic yards, divide by 27.

The Three-Step Process

Calculating cubic yards follows the same pattern every time:

Step 1 — Calculate volume in cubic feet. Multiply length times width times height (or depth), with every measurement in feet.

$V = L \times W \times H \quad (\text{all in feet})$

Step 2 — Divide by 27 to convert to cubic yards.

$\text{Cubic yards} = \frac{V}{27}$

Step 3 — Add a waste factor. Materials compress, spill, and settle. Add 10 percent for most projects:

$\text{Order amount} = \text{Cubic yards} \times 1.10$

That is the entire method. The rest of this page is practice applying it.

Converting Inches to Feet

Thickness for slabs, mulch beds, and gravel layers is almost always given in inches. You must convert to feet before multiplying.

$\text{feet} = \frac{\text{inches}}{12}$

Common conversions you will use repeatedly:

Worked Examples

Example 1: Concrete slab — 12 ft by 10 ft by 4 inches thick

A homeowner wants to pour a concrete pad for a shed. The slab is 12 ft long, 10 ft wide, and 4 inches thick.

Step 1 — Convert inches to feet and find the volume in cubic feet:

$4 \text{ in} = \frac{4}{12} = \frac{1}{3} \text{ ft}$

$V = 12 \times 10 \times \frac{1}{3} = 40 \text{ ft}^3$

Step 2 — Convert to cubic yards:

$\frac{40}{27} \approx 1.48 \text{ yd}^3$

Step 3 — Add 10% overage:

$1.48 \times 1.10 = 1.63 \text{ yd}^3$

Answer: Order approximately 1.63 cubic yards. Since concrete is typically sold in half-yard increments, round up to 2 cubic yards.

Example 2: Mulch bed — 20 ft by 8 ft by 3 inches deep

A gardener is covering a rectangular flower bed with mulch, 3 inches deep.

Step 1 — Convert and calculate volume:

$3 \text{ in} = \frac{3}{12} = 0.25 \text{ ft}$

$V = 20 \times 8 \times 0.25 = 40 \text{ ft}^3$

Step 2 — Convert to cubic yards:

$\frac{40}{27} \approx 1.48 \text{ yd}^3$

Step 3 — Add 10% overage:

$1.48 \times 1.10 = 1.63 \text{ yd}^3$

Answer: Order approximately 1.63 cubic yards of mulch, or round up to 2 cubic yards.

Example 3: Gravel driveway — 40 ft by 12 ft by 6 inches deep

A driveway needs a 6-inch layer of gravel.

Step 1 — Convert and calculate volume:

$6 \text{ in} = \frac{6}{12} = 0.5 \text{ ft}$

$V = 40 \times 12 \times 0.5 = 240 \text{ ft}^3$

Step 2 — Convert to cubic yards:

$\frac{240}{27} \approx 8.89 \text{ yd}^3$

Step 3 — Add 10% overage:

$8.89 \times 1.10 = 9.78 \text{ yd}^3$

Answer: Order approximately 9.78 cubic yards of gravel — round up to 10 cubic yards.

Example 4: Topsoil for an L-shaped garden (irregular shape)

A garden bed is L-shaped. The long arm is 15 ft by 4 ft, and the short arm is 8 ft by 6 ft. The topsoil will be 4 inches deep.

Strategy: Break the irregular shape into two rectangles and add their volumes.

Rectangle A: $15 \times 4 = 60 \text{ ft}^2$

Rectangle B: $8 \times 6 = 48 \text{ ft}^2$

Total area: $60 + 48 = 108 \text{ ft}^2$

Step 1 — Convert depth and find volume:

$4 \text{ in} = \frac{1}{3} \text{ ft}$

$V = 108 \times \frac{1}{3} = 36 \text{ ft}^3$

Step 2 — Convert to cubic yards:

$\frac{36}{27} \approx 1.333 \text{ yd}^3$

Step 3 — Add 10% overage:

$1.333 \times 1.10 = 1.47 \text{ yd}^3$

Answer: Order approximately 1.47 cubic yards of topsoil — round up to 1.5 cubic yards.

Example 5: Concrete for a round pad — diameter 10 ft, 4 inches thick

A circular concrete pad for a hot tub has a diameter of 10 ft and is 4 inches thick. Since the base is a circle, use the formula for the volume of a cylinder: $V = \pi r^2 h$.

Step 1 — Find the radius and convert depth:

$r = \frac{10}{2} = 5 \text{ ft}, \quad h = \frac{4}{12} = \frac{1}{3} \text{ ft}$

Step 2 — Calculate volume in cubic feet:

$V = \pi (5)^2 \times \frac{1}{3} = \pi \times 25 \times \frac{1}{3} = \frac{25\pi}{3} \approx 26.18 \text{ ft}^3$

Step 3 — Convert to cubic yards:

$\frac{26.18}{27} \approx 0.97 \text{ yd}^3$

Step 4 — Add 10% overage:

$0.97 \times 1.10 = 1.07 \text{ yd}^3$

Answer: Order approximately 1.07 cubic yards of concrete — round up to 1.5 cubic yards to be safe with a circular pour.

Quick Reference Table

Common project sizes and their approximate cubic yardage (before overage):

Each value was calculated as: $\frac{L \times W \times (D/12)}{27}$.

How Much Does a Cubic Yard Cover?

Sometimes you know how deep you want a material and need to figure out how much area one cubic yard will cover. Since 1 yd$^3$ = 27 ft$^3$, the coverage area depends on the depth:

$\text{Coverage (ft}^2\text{)} = \frac{27}{\text{depth in feet}}$

For example, if you have a 300 ft² flower bed and want 3 inches of mulch, you need $\frac{300}{108} \approx 2.78$ cubic yards — order 3 cubic yards.

Real-World Application: Ordering Concrete for a Patio

A homeowner is building a 16 ft by 14 ft patio with 4-inch-thick concrete. Here is the complete calculation from start to finish:

Step 1 — Convert thickness to feet:

$4 \text{ in} = \frac{4}{12} = \frac{1}{3} \text{ ft}$

Step 2 — Calculate volume in cubic feet:

$V = 16 \times 14 \times \frac{1}{3} = \frac{224}{3} = 74.67 \text{ ft}^3$

Step 3 — Convert to cubic yards:

$\frac{74.67}{27} = 2.77 \text{ yd}^3$

Step 4 — Add 10% overage:

$2.77 \times 1.10 = 3.05 \text{ yd}^3$

Step 5 — Round up for ordering: Concrete trucks deliver in half-yard or whole-yard increments. Order 3.5 cubic yards to ensure you have enough material. Running short mid-pour creates a cold joint (a weak seam in the concrete), so it is always better to have a small amount left over than to come up short.

Practice Problems

Test your understanding with these problems. Click to reveal each answer.

Key Takeaways

• 1 cubic yard = 27 cubic feet — this is the essential conversion factor ($3 \times 3 \times 3 = 27$)
• The formula is always the same: find the volume in cubic feet ($L \times W \times H$), then divide by 27
• Convert inches to feet first by dividing by 12 — thickness in inches is the most common source of errors
• For circular areas, use $V = \pi r^2 h$ before dividing by 27
• Add 10% overage to account for waste, spillage, settling, and uneven ground
• For irregular shapes, break the area into rectangles, calculate each volume separately, and add them together
• Always round up when ordering — running short is far more costly than having a little extra

Return to Geometry for more topics in this section.