How to Calculate Cubic Yards (With Examples for Any Shape)

By the Mulch Calculator team · Published October 24, 2026 · Facts checked against the sources listed below · About us

Before you order. Results are estimates. Bulk material settles, and loads vary by supplier, so check the bag label or ask your supplier for the real volume and weight. Call 811 before you dig. Keep mulch off tree trunks and away from your house foundation, as UC extension advice explains.

Mulch, topsoil, gravel and concrete are all sold by the cubic yard. Yet most of us measure our yards in feet and inches. On r/HomeImprovement and r/landscaping, people ask how to turn a grading project or a hole on a hill into an order. The answer is one formula and a little care with units.

The short answer

Measure length, width and depth in feet. Multiply them to get cubic feet. Divide by 27 to get cubic yards. If you measured depth in inches, multiply square feet by the inches and divide by 324 instead.

Cubic yards = length (ft) x width (ft) x depth (ft) / 27

Cubic yards = square feet x depth (in) / 324

Why 27 and 324?

A yard is 3 feet. A cubic yard is a cube 3 feet on each side, so it holds 3 x 3 x 3 = 27 cubic feet. The New Hampshire DES conversion sheet lists the same thing, and adds that a cubic yard is 36 x 36 x 36 inches, or 46,656 cubic inches.

The 324 comes from 27 x 12. It lets you skip turning inches into feet. A cubic yard spread 1 inch thick covers 324 square feet. UC Marin Master Gardeners round this to about 325 square feet in their mulch guide.

Step by step for a rectangle

Measure the length in feet.
Measure the width in feet.
Measure the depth. Write it in inches.
Turn inches into feet. Divide by 12. So 4 inches is 0.333 feet.
Multiply length x width x depth. That is cubic feet.
Divide by 27. That is cubic yards.

Example: a garden bed

A bed is 16 feet long and 5 feet wide. You want 3 inches of mulch.

16 x 5 = 80 square feet.
3 / 12 = 0.25 feet.
80 x 0.25 = 20 cubic feet.
20 / 27 = 0.74 cubic yards.

Check with the short form: 80 x 3 / 324 = 0.74. Same answer.

Other shapes

Circle

Area = 3.1416 x radius x radius

The radius is half the distance across. A round bed 10 feet across has a radius of 5 feet. Its area is 3.1416 x 5 x 5 = 78.5 square feet. At 4 inches deep, that is 78.5 x 4 / 324 = 0.97 cubic yards.

Ring

For mulch around a tree, find the area of the outer circle and take away the bare circle at the trunk. Our mulch calculator has a ring shape for this.

Triangle

Area = base x height / 2

A corner bed with a base of 8 feet and a height of 6 feet is 8 x 6 / 2 = 24 square feet.

Odd shapes

Split the area into rectangles, circles and triangles. Find each area, then add them. For a curvy bed, you can also lay a grid of 1 foot squares with string and count them. Count a square if it is at least half inside the bed.

Uneven depth and slopes

Real ground is rarely flat. For a low spot or a slope, take depth readings in a grid across the area, maybe every few feet. Add the readings and divide by how many you took. Use that average depth in the formula.

For a deep hole, like the one on a hill in the r/landscaping thread, think of it as a stack of simple shapes. A rough box for the main part and a wedge for the slope is often close enough. Then add a margin, since fill dirt settles once it is packed.

Unit conversions

From	To	Do this
Inches	Feet	Divide by 12
Cubic feet	Cubic yards	Divide by 27
Cubic yards	Cubic feet	Multiply by 27
Cubic inches	Cubic yards	Divide by 46,656
Cubic yards	US gallons	Multiply by about 202
Cubic yards	Cubic meters	Multiply by 0.7646
Cubic meters	Cubic yards	Multiply by 1.308

The meter figures come from the exact length of a yard, 0.9144 meters, cubed.

Cubic yards per 100 square feet

Depth	Cubic feet	Cubic yards
1 inch	8.3	0.31
2 inches	16.7	0.62
3 inches	25	0.93
4 inches	33.3	1.23
6 inches	50	1.85
12 inches	100	3.70

To use it, divide your square feet by 100 and multiply by the number in the last column. A 450 square foot area at 3 inches is 4.5 x 0.93 = 4.2 cubic yards.

Raised beds

A raised bed is a box, so it is easy. Illinois Extension gives the example of a bed 6 feet long, 3 feet wide and 1 foot deep. That is 18 cubic feet, or 18 / 27 = 0.67 cubic yards. The full guide is how much soil you need for a raised bed.

Common mistakes

Mixing inches and feet. If you multiply 10 feet x 10 feet x 3 inches and forget to change the inches, you get 300 instead of 25 cubic feet.
Dividing by 9. That turns square feet into square yards, not cubic feet into cubic yards.
Forgetting settling. Mulch and soil settle. Add about 10%.
Forgetting weight. A yard of soil weighs about 2,000 pounds, says an Ask Extension expert. See how much a yard of gravel weighs for stone.

Let the tool do it

Our cubic yard calculator takes feet, inches, yards or meters and gives cubic yards, cubic feet and cubic meters. It handles rectangles, circles, rings and triangles. For mulch and bag counts, use the mulch calculator. For tons, use the topsoil calculator or the gravel calculator.

Bottom line

Measure in feet, multiply length x width x depth, and divide by 27. If the depth is in inches, use square feet x inches / 324. Split odd shapes into simple ones, average uneven depths, and add a little extra for settling.

Tools for this guide

FAQ

What is the formula for cubic yards?

Cubic yards = length x width x depth, all in feet, divided by 27. If the depth is in inches, use square feet x inches / 324. Both give the same answer.

How do I convert cubic feet to cubic yards?

Divide cubic feet by 27. For example, 54 cubic feet / 27 = 2 cubic yards.

How many square feet are in a cubic yard?

A cubic yard is a volume, so it depends on depth. One cubic yard covers 324 square feet at 1 inch deep, 108 square feet at 3 inches, and 54 square feet at 6 inches.

How do I measure a slope or an uneven hole?

Take depth readings in several spots across the area and average them. Then use the average depth in the formula. For a deep or odd hole, split it into simple shapes and add them up.