Mulch Calculator

Use this mulch calculator to work out how much mulch your garden beds, borders or tree rings need. Enter the size of the area and how deep you plan to spread the mulch. You will see the volume in cubic yards and cubic feet, plus how many bags that comes to. Results are estimates for planning.

Calculate your mulch

Enter your measurements and press Calculate to see your volume, order amount and bags needed.

How to use this calculator

Pick a mode. Choose Dimensions for a rectangular bed, or Area + depth if you already know the area in square feet or square meters.
Enter the size and depth. Choose a unit for each measurement. Depth is in inches by default. Use the ft+in option for a length such as 12 ft 6 in.
Add quantity or extra if needed. Quantity is for several identical beds. Extra (%) is an optional allowance on top of the exact volume.
Press Calculate. Use the order amount for bulk mulch. For bagged mulch, pick your bag size to see how many bags to buy. Copy result saves everything.

Formula

The three measurements the calculator uses. Volume is length × width × depth.

Every measurement is first converted to feet. Then:

Cubic feet = length × width × depth × quantity × (1 + extra ÷ 100)

Cubic yards = cubic feet ÷ 27

Bags = cubic feet ÷ bag size (cubic feet), rounded up to a whole bag

The order amount is the cubic yards rounded up to the next quarter yard. In Area + depth mode, the area replaces length × width. Inches are divided by 12 to get feet, and we divide by 27 because one cubic yard is 3 ft × 3 ft × 3 ft.

Worked example

A bed measures 10 ft × 10 ft and the mulch will be spread 3 inches deep. (3 inches is just an example.)

Depth: 3 in ÷ 12 = 0.25 ft
Cubic feet: 10 × 10 × 0.25 = 25 cubic feet
Cubic yards: 25 ÷ 27 = 0.93 cubic yards, so an order amount of 1.00 cubic yard
Bags of 2 cubic feet: 25 ÷ 2 = 12.5, rounded up to 13 bags

How far does mulch go?

The deeper you spread mulch, the less ground it covers. This table shows the area covered by one cubic yard and by one 2 cubic foot bag at each depth. A 3 cubic foot bag covers half as much again as a 2 cubic foot bag, and a 1.5 cubic foot bag covers three quarters as much.

Area covered by mulch
Depth	Per cubic yard (sq ft)	Per 2 cu ft bag (sq ft)
1 in	324	24
2 in	162	12
3 in	108	8
4 in	81	6

How deep should mulch be?

Extension services publish depth guidance for garden beds, and it varies a little by material. Three examples:

Utah State University Extension: organic mulch 3 to 4 inches deep and inorganic mulch, such as rock, 2 to 3 inches. It also advises leaving a few inches of mulch-free area around the base of woody plants (Water-Wise Landscaping: Mulch, H. Kratsch).
University of Illinois Extension: 2 to 3 inches once the mulch has settled (Landscape mulch with expectations, R. Hentschel, 2018).
University of Wisconsin–Madison Division of Extension: about 3 inches for most organic mulches (Mulches for Home Gardens and Plantings, H. Harrison, last revised 2011).

Your plants, soil and climate matter, so check with your local extension office. Then enter the depth you choose into the calculator above.

Measuring an irregular area

Not every bed is a neat rectangle. Work out the area first, then enter it in Area + depth mode.

Split it into rectangles. Break an L-shaped bed into rectangles, multiply length by width for each, and add the areas.
Add circles. For a round bed, area = π × radius × radius. For a ring around a tree, subtract the inner circle: area = π × (outer radius² − inner radius²).
Average a slope. If the mulch depth changes steadily from one side to the other, add the shallow and deep depths and divide by 2. Use that average as the depth.

For example, a 12 ft × 8 ft bed (96 sq ft) with a 6 ft round bed beside it (28.27 sq ft) gives a total area of about 124.27 sq ft.

Assumptions and limitations

The bed is a simple box (rectangular) with the same depth everywhere.
The result is the volume of mulch only. It does not account for the type of mulch, or how it breaks down over time.
Bag counts use the size printed on the bag, and bags are rounded up to whole bags.
Suppliers often sell in ¼ or ½ yard steps, so round up to the next step when ordering bulk mulch.
The Extra (%) field is your own allowance. We do not suggest a specific percentage.
Depth guidance on this page is from the extension sources named above. It is general advice, not a recommendation for your site.
Results are estimates for planning. Check quantities with your supplier before ordering.

Frequently asked questions

How many bags of mulch are in a cubic yard?

A cubic yard is 27 cubic feet. That is 13.5 bags of 2 cubic foot mulch, 18 bags of 1.5 cubic foot mulch, or 9 bags of 3 cubic foot mulch. Check the size printed on the bag, because bag sizes vary by brand.

How do I calculate how much mulch I need for a flower bed?

Measure the length and width of the bed, choose how deep you want to spread the mulch, and enter all three above. For a curved bed, work out its area first and use the Area + depth mode.

How many square feet does a cubic yard of mulch cover?

It depends on the depth. One cubic yard covers about 324 square feet at 1 inch deep, 162 at 2 inches, 108 at 3 inches and 81 at 4 inches.

Should I buy mulch in bags or in bulk?

Bagged mulch is sold by the cubic foot and bulk mulch by the cubic yard, so compare prices on the same basis: one cubic yard is 27 cubic feet. Use the bags result if you are buying bagged mulch, and the order amount if you are ordering in bulk. Prices and delivery options vary by supplier.

Should I add extra for settling?

Mulch can settle after it is spread. University of Illinois Extension describes its recommended depth as measured once the mulch has settled, so you may want a small allowance. The Extra (%) field adds whatever percentage you choose. We do not suggest a specific figure.

How do I measure a curved or irregular bed?

Split the bed into simple shapes such as rectangles and circles, work out each area, and add them together. See the section on measuring an irregular area below for an example.