Mulching: How Much Mulch You Need and How Deep to Spread It

What It Means

Mulching is covering the soil around trees, shrubs and garden plants with a layer of material, most often organic mulch such as shredded bark or wood chips. The extension guides we checked from Penn State, the University of Illinois and Colorado State University call for a layer 2 to 4 inches deep, pulled back from tree trunks. Buying the right amount comes down to one conversion: square feet times depth in inches, divided by 324, gives cubic yards.

Try It: Work Out Mulch for One Bed

Enter the size of the bed and the depth you want. Every number updates as you type.

Length (feet)Width (feet)Depth (inches)

Area (sq ft)200

Cubic yards1.85

2 cu ft bags25

Within the 2 to 4 inches the extension guides call for.

How It Sounds at Home

"We need another yard of mulch for the front beds."
"Pull the mulch back off the tree trunk, it's piled way too high."
"How many bags does it take to cover this?"

The Breakdown

The formula. One cubic yard is 27 cubic feet, which covers 324 square feet at 1 inch deep (27 times 12). So cubic yards = square feet × depth in inches ÷ 324. For bagged mulch, square feet × depth in inches ÷ 12 gives cubic feet, and dividing that by the bag size gives the number of bags.

Worked example

Bed	Area	Depth	Cubic yards	Cubic feet	2 cu ft bags
Front bed, 20 ft × 10 ft	200 sq ft	3 in	1.85	50	25
Side bed, 12 ft × 8 ft	96 sq ft	2 in	0.59	16	8
Both beds	296 sq ft		2.44	66	33

The front bed works out as 200 × 3 ÷ 324 = 1.85 cubic yards. Bought in bulk by the cubic yard, both beds need about 2.5 yards; bought in bags, they need 33 bags of 2 cubic feet.

What the result means. Buhata's own suggestion: round up a little rather than down, since beds are rarely perfect rectangles and a short load means a second trip.

Good to Know

Keep mulch off tree trunks. The extension guides we checked say to leave the root flare, where the trunk widens at the base, visible above the mulch. Mulch heaped against a trunk, sometimes called volcano mulching, can cut off oxygen and water to the roots and lead to the tree's decline or death. To stay within 2 to 4 inches overall, measure how deep last year's mulch still is before you add more.

FAQ

How deep should mulch be?

The extension guides we checked from Penn State, the University of Illinois and Colorado State University call for 2 to 4 inches of organic mulch.

How many bags of mulch make a cubic yard?

A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cubic feet, or 9 bags of 3 cubic feet.

Should mulch touch the tree trunk?

No. Pull it back so the root flare shows. Mulch piled against the trunk, called volcano mulching, can starve the roots of oxygen and water.

Do It in Buhata

Maintenance (Household X) and Shopping

Add the number of mulch bags from the calculator to your Shopping list, and put "Top up mulch in the beds" in Maintenance in the Household X add-on each spring.

Open Buhata

Related Terms and Categories

Composting
Turning food scraps and yard waste into a dark, crumbly soil amendment by letting them break down in a managed pile or bin.
Pruning
Cutting away branches or stems to keep a tree or shrub healthy, safe and in shape, timed to the plant so you don't cut off next season's flowers.
Lawn care schedule
A year-round plan that puts each lawn job, from mowing height to seeding and fertilizing, in the season that suits your type of grass.
Home garden
A garden at home where a household grows some of its own vegetables, herbs or fruit, in the ground, in raised beds or in containers.
Lawn care cost
What a household pays for mowing and other yard work over a season, often priced per visit plus extra jobs such as aeration or leaf cleanup.

Home maintenance and repairs

Sources

Penn State Extension, "Mulching Landscape Trees"; Penn State Extension, "Mulch Volcanoes Are Erupting Everywhere!"; University of Illinois Extension, "Proper Mulching Techniques"; Colorado State University Extension, "Mulching Trees and Shrubs"

Last updated September 30, 2026.