Mulch Calculator - Cubic Yards and 2 cu ft Bags

How much mulch do you actually need?

Mulch is sold two ways: in bags, usually 2 cubic feet each, and in bulk by the cubic yard. Both are volumes, so the job is to turn the area of your beds and the depth you want into cubic feet, then into bags or yards. The calculator does both at once and tells you which way is cheaper for your job.

Measure each bed's length and width in feet. For round tree rings, measure the diameter. For odd-shaped beds, break them into rectangles or estimate the area and use the I know the area option. Add as many beds as you have; the total is what you order.

How deep should mulch be?

University extension services, including Iowa State and Mississippi State, recommend 2 to 4 inches for most landscape beds. Fine mulches like shredded hardwood or pine straw work at 2 to 3 inches. Coarse wood chips can go 3 to 4 inches. Less than 2 inches will not stop weeds; more than 4 can suffocate roots and keep soil soggy.

If you are topping up last year's mulch, measure what is left first. Often an inch refresh is all you need, which cuts the order by two-thirds. And keep mulch 2 to 3 inches away from tree trunks and plant stems. Mulch volcanoes piled against a trunk trap moisture and invite rot and rodents.

The formula

Cubic feet = area in sq ft × (depth in inches ÷ 12). Cubic yards = cubic feet ÷ 27. Bags = cubic feet ÷ bag size, rounded up. A handy shortcut: one cubic yard covers 324 sq ft at 1 inch deep, 162 sq ft at 2 inches, 108 at 3 inches, and 81 at 4 inches. One cubic yard also equals 13.5 bags of 2 cubic feet.

Worked example: one bed vs a whole yard

A 20 × 5 ft bed is 100 sq ft. At 3 inches deep that is 25 cubic feet, or 0.93 cubic yards. In 2-cubic-foot bags, 25 ÷ 2 = 12.5, so you buy 13 bags. At $4 a bag, that is $52. Bulk would be one yard at $40 plus a $60 delivery fee, or $100. Bags win easily.

Now a whole yard of beds totaling 800 sq ft at 3 inches: 200 cubic feet, or 7.4 cubic yards. That is 100 bags, $400, and a lot of plastic. Bulk is 7.5 yards at $40 plus $60 delivery, or $360, and one pile on a tarp instead of 100 trips from the car. The break-even usually lands somewhere around 2 to 3 yards, depending on local bag and bulk prices, which is why the calculator compares both with your numbers.

Choosing mulch

Shredded hardwood knits together and stays put on slopes. Pine bark nuggets last longer but float in heavy rain. Pine straw is light and cheap in the South. Dyed mulch keeps its color a season or two; undyed breaks down faster and feeds the soil. Rubber mulch does not decompose at all, which is good for playgrounds and bad for garden beds. For play areas, safety guidelines typically call for 9 to 12 inches of wood chips or shredded rubber under equipment, well beyond garden depth.

Common mistakes

Using the bag count from the store's sign. Those charts often assume 2 inches. Put your real depth in.

Forgetting settling. Fresh bulk mulch settles by 10% or so in the first few weeks. If you want a firm 3 inches, spread a hair over.

Mulching over weeds. Pull or kill them first, or lay down cardboard or a pre-emergent. Mulch slows new weeds but will not smother established ones.

Burying the root flare. Trees should flare out at the base like a wine glass, not a telephone pole. If the flare is buried, pull mulch back.

When to hire a pro

Spreading mulch is easy, just heavy. A landscaper makes sense when you are covering several thousand square feet, when beds need edging and weeding first, or when you would rather pay about $50 to $100 per yard installed than spend two weekends with a wheelbarrow. Some landscape yards also blow mulch in with a truck-mounted hose, which is fast and even on big jobs.