Mulch Calculator

How It Works

The calculator multiplies your area by your depth in feet to get cubic feet, then divides by 27 to get cubic yards. For bags, it divides cubic feet by the bag size and rounds up, since you cannot buy part of a bag.

Iowa State University Extension says mulch is commonly sold in 2 or 3 cubic foot bags, which is why those are the two buttons above. Texas A&M AgriLife Extension uses the same cubic yard formula, and it rounds bag counts up as well.

See Methods and Sources

Worked Example

Here is the math for a bed that is 20 feet long, 10 feet wide, and 3 inches deep, using 2 cubic foot bags.

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
5. 50 cu ft / 2 cu ft per bag = 25 bags

With 3 cubic foot bags, the same bed takes 17 bags, because 50 divided by 3 is 16.67, which rounds up.

Cubic Yards of Mulch by Area and Depth

Use this table for a quick check before you enter your own numbers.

Bags of Mulch by Area and Depth

These counts use 2 cubic foot bags, rounded up to whole bags.

How Deep Should Mulch Be?

More mulch is not always better, so pick a depth before you buy.

UF/IFAS Gardening Solutions recommends a 2 to 3 inch layer around established trees, shrubs, and bedding plants, and it says not to apply more than 3 inches, because excessive mulch can divert rain and irrigation meant for plant roots. For seedlings and small vegetables or herbs, it suggests only a 1 inch depth. Iowa State University Extension says many hardwood chipped or shredded mulches are spread between 2 and 4 inches thick.

Keep mulch away from plant bases, too. UF/IFAS says to place it about 1 foot from the base of large plants and trees, and to leave a couple of inches free of mulch around smaller plants.

Frequently Asked Questions

These cover the questions that come up most often.