How much mulch do I need?

Multiply square feet by depth in feet and divide by 27 for cubic yards. A 200 sq ft bed at 3 inches needs 1.9 cubic yards, or 25 bags of 2 cubic feet.

How deep should mulch be?

Two to four inches of organic mulch, per Penn State Extension, and 1 to 2 inches if it is fine or double-shredded. Use less on poorly drained soil.

How many bags of mulch are in a cubic yard?

About 13.5 bags of 2 cubic feet, since a cubic yard is 27 cubic feet. Bags come in other sizes, so check the volume printed on yours.

Should I add extra for waste?

Only if you expect spills or uneven ground. The waste field starts at 0 because no published figure fits every bed. A few percent covers spillage on a small job.

Do I subtract the old mulch?

Yes. Measure the existing layer and order only the difference. Adding a full depth on top each year is how beds pass the 4 inch ceiling.

HyreYard tools

Mulch calculator: how many yards you need

Type the bed area and the depth you want. You get cubic yards and 2 cu ft bags, with the arithmetic printed under the result.

2–4 in organic mulch, and no more Penn State Extension, “Mulching Landscape Trees”: 1 to 2 inches for fine or double-shredded mulch, and less on poorly drained soil.

Cubic yards of mulch = square feet × (depth in inches ÷ 12) ÷ 27. A 200 sq ft bed at 3 inches takes 1.9 cubic yards, or 25 bags of 2 cubic feet. Penn State Extension caps organic mulch at 2 to 4 inches, and 1 to 2 inches for fine mulch.

Work out your mulch

Geometry only. Nothing is stored or emailed.

— Cubic yards

— 2 cu ft bags

— Depth check

What this assumed —

Depth means settled depth. Measure the old layer and subtract it before you order.

Start here

Why more mulch can hurt the plant

Too much gravel wastes money. Too much mulch can starve roots of air, and the damage shows years later.

The published figure is a range with a ceiling. Penn State Extension: “Apply a 2- to 4-inch layer of organic mulch and no more; use less if the soil is poorly drained.”

Fine mulch has a lower ceiling. “If using finely textured or double-shredded mulch, use 1 to 2 inches since these materials allow less oxygen through to the root zone.” If you set the calculator to 3 inches and buy double-shredded bark, you have ordered half as much again as the 2-inch limit allows.

The reason is oxygen. Under a deep layer, Penn State writes, “air may not penetrate the mulch layer and the underlying soil becomes depleted of oxygen”. Roots in that soil can die back, and the plant may grow new roots up into the mulch, where they dry out in a drought.

Wet soil needs the thin end. A bare, soggy bed tempts a thicker layer, and a thick layer keeps it wetter still.

What one cubic yard covers at each depth

HyreYard arithmetic: 27 cubic feet divided by the depth in feet. Bag counts use a 2 cu ft bag, a common size. Check yours.

Depth	Sq ft per cubic yard	2 cu ft bags per 100 sq ft	Against Penn State’s guidance
2 in	162 sq ft	9	In range. The ceiling for fine or double-shredded mulch.
3 in	108 sq ft	13	In range for coarse mulch on well-drained soil. Over the limit for fine mulch.
4 in	81 sq ft	17	At the published ceiling.
6 in	54 sq ft	25	Above the ceiling. The calculator will compute it; the guidance does not support it.

Depth means settled depth, measured after rain. Topping up without measuring the old layer is how a bed passes 4 inches.

Keep mulch off the trunk

A cone of mulch piled against a tree is called a mulch volcano. The guidance asks for the opposite shape.

What Penn State recommends

Pull mulch back 3 to 5 inches from young trees and 8 to 10 inches from mature ones, so the root flare shows. The flare is where the trunk widens into roots.

The shape is a flat ring, open in the middle. It takes less material than a cone.

What damp mulch against bark does

Bark above ground is meant to dry out. Held damp against mulch, it stays wet, which invites decay and gives rodents cover to chew the stem in winter.

Roots can also grow into the pile and circle the trunk. These girdling roots tighten slowly, so the cause is easy to miss.

Fixing an existing volcano

Rake it back until the flare shows. If you cannot find a flare at all, the tree may have been planted too deep, which is a question for an arborist.

It needs a rake and a few minutes, not a contractor.

How to spread it so the number stays true

The calculator assumes an empty bed and a flat layer. These steps make that true.

1
Measure what is already there
Push a trowel down to soil and measure the old layer. Subtract it from your target depth before you order.
2
Pick the depth from the material
Coarse bark or wood chips: 2 to 4 in. Fine or double-shredded: 1 to 2 in. Poorly drained soil: less.
3
Break up the old crust
Fine mulch can mat into a crust that sheds rain. Rake the old layer loose before you add more.
4
Spread wide and flat
Take the ring out toward the drip line, where the roots are. Check depth with a ruler in three places.
5
Clear the trunk and crowns
Leave 3 to 5 in bare around young trees and 8 to 10 in around mature ones. Keep mulch off shrub crowns and perennial stems too.
6
Keep it off paving and drains
Mulch that washes onto a patio stains it and can block a drain. On a slope toward paving, use a thinner layer of coarser material.

What to ask before the mulch is delivered

Bulk mulch comes with no standard label, so ask.

What is it made of?
Bark, whole-tree chips, ground pallets and yard-waste compost are all sold as mulch. Ask which one you are getting.
Is it fine, double-shredded or coarse?
The answer sets your depth: 1 to 2 in for fine, 2 to 4 in for coarse.
How many cubic yards is that?
A “scoop” is a loader bucket, not a unit. Ask for cubic yards, the number this calculator gives you.
Can a tree crew drop chips?
Arborist chips are coarse and mixed, and some crews will drop a load at no charge. You get the whole load, not a measured amount.
A quote priced “per bed”
You cannot check depth against volume. Ask for cubic yards and the intended depth in writing.
Mulch piled against trunks
Penn State asks for the flare to be left bare. A crew that builds cones is not following that guidance.

Mulch terms on a quote or a bag

Root flare: Where the trunk widens into roots. It should sit above ground and stay visible.
Drip line: The circle on the ground under the outer edge of the canopy. A useful edge for a mulch ring.
Girdling root: A root that circles the trunk and slowly squeezes it. It can grow in mulch piled against the stem.
Double-shredded: Ground twice for a fine texture. It mats easily and has the lower 1 to 2 in depth limit.
Arborist chips: Whole-tree chips from a tree crew’s chipper: leaves and wood, coarse and mixed.
Settled depth: Depth after rain has compressed the layer. Measure a few weeks after spreading.
Inorganic mulch: Stone, rubber or glass. It does not break down, so it adds nothing to the soil and does not need topping up.

Check whether your soil drains

“Use less if the soil is poorly drained” only helps if you know which soil you have.

Web Soil Survey, from USDA Natural Resources Conservation Service, returns the mapped soil under a boundary you draw, with its drainage class and hydrologic soil group. It is free and needs no account.

What to read. If the drainage class is “somewhat poorly drained” or worse, sit at the bottom of the depth range. Hydrologic group D soils shed the most water.

The test in your own bed. Dig a hole a foot deep, fill it, let it drain, fill it again and time it. Water still standing hours later means a thinner layer, whatever the map says.

What this calculator cannot see

The material. It will compute 4 inches of double-shredded bark, which is twice the 2-inch limit for fine mulch.

The old layer. It assumes an empty bed. Measure what is there and subtract it.

Your soil and plants. It is a volume, not a planting plan or a price. HyreYard does not sell, deliver or spread mulch. Figures checked 5 September 2026.

Questions this calculator answers

How much mulch do I need?: Multiply square feet by depth in feet and divide by 27 for cubic yards. A 200 sq ft bed at 3 inches needs 1.9 cubic yards, or 25 bags of 2 cubic feet.
How deep should mulch be?: Two to four inches of organic mulch, per Penn State Extension, and 1 to 2 inches if it is fine or double-shredded. Use less on poorly drained soil.
How many bags of mulch are in a cubic yard?: About 13.5 bags of 2 cubic feet, since a cubic yard is 27 cubic feet. Bags come in other sizes, so check the volume printed on yours.
Should I add extra for waste?: Only if you expect spills or uneven ground. The waste field starts at 0 because no published figure fits every bed. A few percent covers spillage on a small job.
Do I subtract the old mulch?: Yes. Measure the existing layer and order only the difference. Adding a full depth on top each year is how beds pass the 4 inch ceiling.
How far should mulch stay from a tree trunk?: Penn State says 3 to 5 inches from young trees and 8 to 10 inches from mature ones, so the root flare stays visible.

Sources and methodology

Figures dated September 5, 2026. Last reviewed September 18, 2026.

Mulching Landscape Trees (Penn State Extension, retrieved September 5, 2026). Depth guidance: 2 to 4 in of organic mulch, 1 to 2 in for fine or double-shredded, less on poorly drained soil; mulch held 3 to 5 in from young trunks and 8 to 10 in from mature ones.
Web Soil Survey (USDA Natural Resources Conservation Service, retrieved September 5, 2026). Free lookup of the mapped soil and its drainage class. A survey map, not a test of your bed.

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