How to Calculate Cubic Yards

Cubic Yards by Area and Depth

Use this table for a quick check. Find your area on the left and your depth across the top.

The Formula

A cubic yard is a cube 3 feet long on each side, so it holds 3 x 3 x 3, or 27, cubic feet. NIST Handbook 44 lists the same figure. Work in feet, then divide by 27.

Length and width are in feet, and depth is in inches. Dividing the depth by 12 turns inches into feet. Forgetting that step is the most common mistake, because a 3 inch depth entered as 3 feet gives an answer 12 times too large.

Worked Example: A Rectangle

Here is the math for an area 20 feet long, 10 feet wide, and 3 inches deep.

1. 20 ft x 10 ft = 200 sq ft
2. 3 in / 12 = 0.25 ft
3. 200 sq ft x 0.25 ft = 50 cu ft
4. 50 cu ft / 27 = 1.85 cu yd

Worked Example: A Circle

For a round bed, find the area first with pi times the radius squared. The radius is half the width across. Here is a bed 12 feet across and 4 inches deep.

1. 12 ft / 2 = 6 ft radius
2. 3.14 x 6 ft x 6 ft = 113.04 sq ft
3. 113.04 sq ft x 4 in / 12 = 37.68 cu ft
4. 37.68 cu ft / 27 = 1.40 cu yd

Worked Example: A Triangle

For a triangle, the area is half the base times the height. Here is a corner bed with a 10 foot base, an 8 foot height, and a depth of 3 inches.

1. 10 ft x 8 ft / 2 = 40 sq ft
2. 40 sq ft x 3 in / 12 = 10 cu ft
3. 10 cu ft / 27 = 0.37 cu yd

How Far One Cubic Yard Goes

Divide 324 by the depth in inches to see how many square feet one cubic yard covers. The 324 comes from 27 cubic feet times 12 inches per foot.

Typical Depths by Project

The depth you pick drives the answer, so start from guidance for your job. These are starting points from the sources below, not rules.

For a 200 square foot bed, 2 inches of mulch is 1.23 cubic yards, and 4 inches is 2.47 cubic yards.

From Cubic Yards to Bags

Bags of mulch and soil usually list their size in cubic feet, so turn yards back into feet. Concrete mix is sold by weight, so use the yield printed on the bag instead. Multiply cubic yards by 27, then divide by the bag size. Round up, since you cannot buy part of a bag. Here is the first example again, with a 2 cubic foot bag.

1. 50 cu ft, the volume from the first example
2. 50 cu ft / 2 cu ft per bag = 25 bags

Check the size on the bag, since sizes differ by product.

What Changes the Number

Depth matters as much as area, so measure it with care. Doubling the depth doubles the volume, the same as doubling the area.

Uneven ground is the next problem. Measure the depth in several spots, and use the average. For odd shapes, split the area into rectangles and circles, work out each one, and add them up.

Loose material can also settle after you spread it. The University of Kentucky lawn guide says a newly graded lawn should be allowed to settle before planting, so ask your supplier how much to order for your finished depth.

Cubic yards measure volume, not weight, so the same volume of two materials can weigh different amounts. Use a calculator for your material when you need tons.

Frequently Asked Questions

These cover the questions that come up most often.