Calculators

Mulch Calculator

Cubic yards and bags of mulch for a garden bed or tree ring, with the cost in bags and in bulk.

How it works

Multiply the bed's area by the depth in feet to get cubic feet, and divide by 27 for cubic yards, which is how bulk mulch is sold. Bags are sold by the cubic foot, usually 2 cu ft, so divide the cubic feet by the bag size. For a ring around a tree, the area is π × (diameter ÷ 2)².

cubic yards = area (sq ft) × depth (in) ÷ 12 ÷ 27
27
Cubic feet in a cubic yard
Depth
2–3 in for most beds, 1 in to top up
Bag
Usually 2 cu ft; 13.5 bags make a cubic yard

Worked example

A 20 × 10 ft bed mulched 3 in deep. Bags are $4.50 for 2 cu ft; bulk is $40 a yard.

  1. 1Area: 20 × 10 = 200 sq ft
  2. 2Volume: 200 × 3 ÷ 12 = 50 cu ft
  3. 3Cubic yards: 50 ÷ 27 = 1.85
  4. 4Bags: 50 ÷ 2 = 25 bags, $112.50
  5. 5Bulk: 1.85 × $40 = $74, before delivery

About 1.85 cubic yards, or 25 bags. Bulk is cheaper once delivery costs less than the $38 difference.

Frequently asked questions

How deep should mulch be?

Two to three inches for most beds. Less than 2 in lets weeds through; more than 4 in can starve roots of air and keep the soil too wet. Top up an existing bed by only an inch or so a year, as the old layer breaks down.

How many bags of mulch are in a yard?

13.5 bags of 2 cu ft, or 9 bags of 3 cu ft. A cubic yard covers about 108 sq ft at 3 in deep, 162 sq ft at 2 in, or 324 sq ft at 1 in.

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

Bulk is usually half the price per yard or less, but delivery often costs $30–$75 and many suppliers have a 2–3 yard minimum. For a yard or two, bags or a pickup-truck load from the yard may cost less overall.

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