How to Calculate Cubic Yards: Concrete, Mulch & Square Feet Conversion

The formula for calculating cubic yards is:

Cubic yards = (Length × Width × Depth in feet) ÷ 27

The most common mistake is mixing units. Length and width are usually in feet, but depth is often in inches (like a 4-inch concrete slab or 3-inch mulch layer). Convert inches to feet first by dividing by 12 — a 4-inch slab is 0.333 feet, a 6-inch layer is 0.5 feet. Only after all three dimensions are in feet can you multiply them together.

The shortcut formula combines the inch-to-feet and cubic-feet-to-yards conversions into one step:

Cubic yards = Square feet × Depth (inches) ÷ 324

The 324 comes from 27 × 12. For 200 sq ft at 4 inches: 200 × 4 ÷ 324 = 2.47 cubic yards — the same result as the long method.

If you already know your area in square feet, the conversion is straightforward. You need a depth to convert area (2D) into volume (3D):

1. Multiply square footage by the depth in feet.
2. Divide by 27 to get cubic yards.

Example: 200 sq ft at 4 inches deep: 200 × (4 ÷ 12) = 66.67 cubic feet ÷ 27 = 2.47 cubic yards.

For a rectangular concrete slab, multiply length × width × thickness (all in feet), then divide by 27. Add 5–10% for waste and uneven subgrades.

Example: A 10 × 10 foot slab at 4 inches thick: 10 × 10 × 0.333 = 33.3 cubic feet ÷ 27 = 1.23 cubic yards. With 10% waste, order 1.36 cubic yards.

Once you have cubic yards, decide between ready-mix delivery and bagged concrete. Ready-mix is more cost-effective above about 1.5 cubic yards. For smaller jobs, use the bag table below.

Example: A 12 × 12 patio slab at 4 inches = 1.78 cubic yards. With 10% waste, order 1.95 cubic yards — or about 88 eighty-pound bags for a bagged pour.

Mulch is typically applied 2–4 inches deep. Calculate bed area (length × width in feet) × depth in feet ÷ 27 for cubic yards. Most bagged mulch is 2 cubic feet, so one cubic yard equals about 13.5 bags.

Example: A 200 sq ft bed at 3 inches deep: 200 × 0.25 = 50 cubic feet ÷ 27 = 1.85 cubic yards. In bags: 50 ÷ 2 = 25 bags of 2 cu ft mulch.

Dirt uses the same volume formula: length × width × depth in feet ÷ 27. A 10 × 8 raised bed at 12 inches deep needs 10 × 8 × 1 = 80 cubic feet ÷ 27 = 2.96 cubic yards. Always add 15–25% for settling — topsoil settles 20–30%, fill dirt 10–15%.

Example: A 20 × 10 grading area at 6 inches: 20 × 10 × 0.5 = 100 cubic feet ÷ 27 = 3.70 cubic yards. With 15% settling, order 4.26 cubic yards. Loose topsoil weighs about 1.0 US tons per cubic yard; fill dirt 1.1–1.25 tons. See our dirt calculator for details.

Gravel uses the same formula: area × depth ÷ 27. A 20 × 10 driveway at 4 inches: 20 × 10 × 0.333 = 66.7 cubic feet ÷ 27 = 2.47 cubic yards. Add 10–15% for compaction — loose gravel compacts about 20%.

At a typical density of 1.4 US tons per cubic yard, 2.47 cubic yards of pea gravel = 3.46 US tons. For a 2-car driveway (500 sq ft) at 6 inches, expect 11–14 cubic yards. See our gravel calculator for material-specific estimates.

Soil and topsoil use the standard formula: length × width × depth in feet ÷ 27. For a 500 sq ft lawn at 4 inches: 500 × 0.333 = 166.7 cubic feet ÷ 27 = 6.17 cubic yards. Add 20–25% for settling — loose topsoil compacts significantly.

Loose topsoil weighs about 1.0 US tons per cubic yard (2,000 lb); compacted topsoil is denser at about 1.25 tons. A typical pickup truck safely carries about 1 cubic yard of topsoil.

Sand uses the same volume formula. Loose dry sand weighs about 1.35 US tons per cubic yard. A 10 × 10 paver base at 2 inches: 10 × 10 × 0.167 = 16.7 cubic feet ÷ 27 = 0.62 cubic yards (about 0.84 tons).

Decorative rock and crushed stone typically weigh 1.25–1.35 US tons per cubic yard. For a 50 sq ft landscaping bed at 3 inches: 50 × 0.25 = 12.5 cubic feet ÷ 27 = 0.46 cubic yards.

To convert tons to cubic yards, divide the weight in US tons by the material's density in tons per cubic yard. The same weight gives different volumes — 7 tons of gravel (1.4 tons/cu yd) = 5 cubic yards, but 7 tons of topsoil (1.0 tons/cu yd) = 7 cubic yards.

Use our free tons to cubic yards converter for instant results with material-specific densities.

Dump truck and trailer capacity is measured in cubic yards. A standard pickup truck carries 1–2 cubic yards, a single-axle dump truck holds 2–5 cubic yards, a tandem axle holds 10–16 cubic yards, and a tri-axle holds 15–20 cubic yards. A 10-yard dumpster holds 10 cubic yards, a 30-yard dumpster holds 30.

To check if your material fits, calculate the volume (length × width × depth ÷ 27) and compare to the vehicle's rated capacity. Always account for weight limits — a truck may be full by weight before it's full by volume.

These two units measure volume but at different scales:

• Cubic feet (cu ft): A cube measuring 1 ft × 1 ft × 1 ft. Used for smaller volumes like bagged soil, refrigerator capacity, and appliance specs.
• Cubic yards (cu yd): A cube measuring 3 ft × 3 ft × 3 ft = 27 cubic feet. Used for bulk materials like concrete, mulch, gravel, and fill dirt.

To convert cubic feet to cubic yards, divide by 27. To convert cubic yards to cubic feet, multiply by 27. A 10 × 10 patio is about 11.1 square yards of surface, but at 6 inches deep it is only 1.85 cubic yards of material.

To convert cubic yards to tons, multiply by the material's density. There is no universal conversion factor — each material has its own density.

Example: 5 cubic yards of gravel at 1.4 tons/cu yd = 7.0 US tons. The same 5 cubic yards of mulch at 0.3 tons/cu yd = only 1.5 US tons — a 4.7× difference from the same volume.

For round shapes — fire pits, round slabs, post holes — use the cylinder formula:

Cubic yards = (π × radius² × height) ÷ 27

Measure the radius as half the diameter. Example: A round fire pit 4 feet across (2 ft radius) and 2 feet deep: π × 2² × 2 = 25.13 cubic feet ÷ 27 = 0.93 cubic yards.

For area calculations, use the square footage calculator. For driveway gravel, see the gravel calculator. For instant results, use our free cubic yard calculator.