How to Calculate Cubic Yards of Dirt, Mulch and Topsoil

Published 2026-10-25

Landscape yards sell dirt, mulch, topsoil and compost by the cubic yard, but nobody measures a garden in yards. You measure in feet and inches, so you need a quick way to turn those measurements into the number a supplier asks for. It takes one formula and about a minute.

What a cubic yard is

A cubic yard is a cube 3 feet long, 3 feet wide and 3 feet high. That’s 3 × 3 × 3 = 27 cubic feet. Picture a box a little bigger than a washing machine. Every cubic yard calculation comes down to finding the cubic feet and dividing by 27.

The formula

The step that trips people up is depth. Beds and lawns are measured in inches, so divide the inches by 12 first: 3 inches is 0.25 ft, 4 inches is 0.333 ft, 6 inches is 0.5 ft. If you multiply by 3 instead of 0.25, the answer comes out twelve times too big.

The cubic yard calculator takes length, width and depth in any units and does the conversion for you. The examples below show the math by hand.

Example 1: soil for a raised bed

An 8 × 4 ft raised bed, 12 inches deep:

• 8 × 4 × 1 = 32 cubic feet
• 32 ÷ 27 = 1.19 cubic yards

Fresh, loose soil settles after watering, often by 10% to 20%. Order about 1.3 to 1.4 yards, or plan to top up after the first few weeks.

Example 2: mulch for a garden bed

A bed covering 200 square feet, mulched 3 inches deep:

• 200 × 0.25 = 50 cubic feet
• 50 ÷ 27 = 1.85 cubic yards

Two to three inches of mulch is a common depth for keeping weeds down and holding moisture. Keep it pulled back a few inches from tree trunks and plant stems.

Example 3: topsoil for a new lawn

A 1,000 sq ft lawn area with 4 inches of new topsoil:

• 1,000 × 0.333 = 333 cubic feet
• 333 ÷ 27 = 12.3 cubic yards

That’s a full truckload, which is why bulk delivery makes sense for lawns. Topdressing an existing lawn uses far less, since it’s spread only about a quarter to half an inch thick.

Example 4: filling a hole

A hole 3 feet long, 3 feet wide and 3 feet deep is exactly 1 cubic yard, because it’s the same shape as the definition. If you’re filling a hole where a tree stump was removed, add a little extra and tamp the dirt down in layers so it doesn’t sink later.

Round and odd-shaped areas

• Circle: area = 3.14 × radius × radius. A round bed 10 feet across has a radius of 5 ft, so 3.14 × 5 × 5 = 78.5 sq ft. At 3 inches of mulch: 78.5 × 0.25 = 19.6 cu ft, or 0.73 cubic yards.
• Triangle: area = base × height ÷ 2.
• Irregular shapes: split them into rectangles, circles and triangles, work out each one, and add them together. Rounding up slightly covers the curves.

Bags or bulk?

Garden centers sell mulch and soil in bags measured in cubic feet. To see how many bags equal one cubic yard, divide 27 by the bag size:

The mulch bed in Example 2 needs 25 bags of 2 cubic feet. For a job much over a cubic yard or two, bulk delivery is usually cheaper and saves a lot of lifting, though it often comes with a delivery fee and a minimum order.

Dirt vs gravel vs concrete

Dirt, mulch, topsoil and compost are sold by volume, so cubic yards are all you need. Gravel and stone are often sold by weight, so you’ll need to convert yards to tons; our guide on how much stone you need and the gravel calculator handle that. For concrete, the concrete calculator gives both cubic yards and the number of bags.

Common questions

• How many square feet does a cubic yard cover? 324 sq ft at 1 inch deep, 162 sq ft at 2 inches, 108 sq ft at 3 inches and 81 sq ft at 4 inches.
• How much does a cubic yard of dirt weigh? Usually around a ton or more, depending on the soil and how wet it is. Check that a pickup or trailer can carry it before you collect a load yourself.
• Will a cubic yard fit in a pickup truck? Many full-size pickups can hold a cubic yard by volume, but a yard of wet soil can be heavier than the truck is rated to carry. Ask the supplier, and check your truck’s payload.
• Should I round up? Yes. Suppliers usually sell in half or whole yards, and running short means a second delivery fee.