Mulch Calculator — Bags, Yards & Tree Rings

What one 2 ft³ bag covers
Depth	One bag covers	One yd³ covers
2 in	12 ft²	162 ft²
3 in	8 ft²	108 ft²
4 in	6 ft²	81 ft²

What one 2 ft³ bag covers

Depth

One bag covers

One yd³ covers

2 in

12 ft²

162 ft²

3 in

8 ft²

108 ft²

4 in

6 ft²

81 ft²

How to calculate how much mulch you need

Measure each bed — length × width for a rectangle; for a round bed, π × (diameter ÷ 2)².
Choose the depth — 2–3 inches for most beds.
Multiply area × depth ÷ 12 to get cubic feet.
Divide by the bag size for bags, or by 27 for cubic yards.

Worked example. A front bed 20 ft × 4 ft, 3 inches deep:

Area: 20 × 4 = 80 sq ft
Volume: 80 × 3 ÷ 12 = 20 cu ft = 20 ÷ 27 = 0.74 yd³
Bags: 20 ÷ 2 = 10 bags of 2 cu ft, or 7 bags of 3 cu ft

Add every bed and tree as its own area: the calculator keeps each one’s depth, adds them up and shows the step-by-step working. For a bed with an odd outline, the square footage calculator can find its area first.

How far a bag goes

Bag	At 2 in	At 3 in	At 4 in	Bags per cubic yard
1 cu ft	6 sq ft	4 sq ft	3 sq ft	27
1.5 cu ft	9 sq ft	6 sq ft	4.5 sq ft	18
2 cu ft	12 sq ft	8 sq ft	6 sq ft	13.5
3 cu ft	18 sq ft	12 sq ft	9 sq ft	9

One cubic yard of bulk mulch covers 162 sq ft at 2 inches, 108 sq ft at 3 inches and 81 sq ft at 4 inches. Metric bags are sold in liters: a 2 cu ft bag is about 56 L, a 3 cu ft bag about 85 L.

How deep to spread mulch

Guidance	Depth	Source
Around trees	2–3 in, in a circle at least 3 ft across	University of Illinois Extension
Trees and shrubs	1–3 in	University of Maryland Extension
Coarse arborist wood chips	3–4 in, never more than 4 in	Oregon State University Extension
Bark mulch	no more than 3 in	Oregon State University Extension

Fine, shredded mulch packs down and needs less depth; coarse chips stay open and need a little more to block light. The Depth for all beds buttons set 2, 3 or 4 inches everywhere at once, and the calculator warns above 4 inches.

Mulch around trees: rings, not volcanoes

All three extension services say the same thing: keep mulch off the trunk. Maryland advises about 3 inches of clearance, Illinois at least 4; mulch piled against the bark keeps it wet and invites disease, and Oregon State notes it shelters voles that chew the bark.

That is why the calculator has a Tree ring shape. Enter the outer diameter of the ring — at least 3 feet — and the bare circle around the trunk, and only the ring itself is counted. A 6 ft ring with a 1 ft bare circle, 3 inches deep, takes 6.9 cu ft: about 3½ bags of 2 cu ft per tree. Put the number of similar trees under Identical trees.

Topping up old mulch

Organic mulch decomposes and has to be replenished as it breaks down, as Illinois Extension puts it. You do not need a full new layer, only the difference. Measure what is left (poke a ruler into the bed), enter it under Mulch already there, and the calculator orders only what is missing: 1 inch left with a 3 inch target means adding 2 inches, a third less mulch than starting over.

Common jobs

All figures are at 3 inches without extra; bags are rounded up.

Job	Area	Cubic yards	Bulk order	2 cu ft bags	3 cu ft bags
Front bed, 20 × 4 ft	80 sq ft	0.74	1 yd³	10	7
Long border, 30 × 6 ft	180 sq ft	1.67	2 yd³	23	15
5 tree rings, 6 ft across, 1 ft bare at the trunk	137 sq ft	1.27	1.5 yd³	18	12
All beds in a typical yard	500 sq ft	4.63	5 yd³	63	42
Yearly top-up of those beds, 1 in → 3 in	500 sq ft	3.09	3.5 yd³	42	28

Bags or bulk

Bags are tidy, easy to carry and right for a few beds. Bulk mulch is delivered by the cubic yard — the calculator rounds your order up to the next half yard, the usual delivery step — and usually costs less per yard once you need more than one or two yards. Put a bag price or a bulk price per yard under Price to compare them.

Planting a new bed rather than covering one? Work out the soil with the topsoil calculator, then mulch on top. For gravel paths between beds, use the gravel calculator; for any other loose material, the cubic yards calculator.

Frequently asked questions

How many bags of mulch are in a cubic yard?

13.5 bags of 2 cu ft — buy 14 — or 9 bags of 3 cu ft, 18 bags of 1.5 cu ft and 27 bags of 1 cu ft. A cubic yard is 27 cubic feet, so divide 27 by the bag size.

How much area does a bag of mulch cover?

A 2 cu ft bag covers 12 sq ft at 2 inches deep, 8 sq ft at 3 inches and 6 sq ft at 4 inches. A 3 cu ft bag covers half as much again: 18, 12 and 9 sq ft. The formula is bag size × 12 ÷ depth in inches.

How deep should mulch be?

About 2–3 inches for most beds and tree rings. University of Illinois Extension recommends a 2 to 3 inch layer around trees, Maryland one to three inches, and Oregon State 3–4 inches only for coarse arborist wood chips, with bark no deeper than 3 inches.

How much mulch do I need for a tree?

Spread it in a circle at least 3 feet across and keep it about 4 inches clear of the trunk, as Illinois Extension advises. A 6 ft ring 3 inches deep with a 1 ft bare circle at the trunk takes 6.9 cu ft — 4 bags of 2 cu ft. Choose the Tree ring shape and enter both diameters.

Should I remove old mulch before adding new?

Usually not. Organic mulch breaks down and needs topping up, but you only add the difference: if 1 inch is left and you want 3, add 2. Enter the depth that is already there under Mulch already there and the calculator orders only what is missing. Rake it loose first if it has matted.

Is it cheaper to buy mulch in bags or in bulk?

Bags are easier for a few beds; bulk delivery usually costs less per yard once you need more than a cubic yard or two — about 14 bags of 2 cu ft per yard. Enter both a bag price and a bulk price per yard to compare for your yard.