How Much Mulch Do I Need?
Multiply the area of your beds by the depth you want, then convert to cubic yards or bags. In feet and inches:
Cubic yards = square feet × depth in inches ÷ 324
The 324 comes from 27 cubic feet in a cubic yard times 12 inches in a foot. For bags, divide cubic feet by the bag size: bags = square feet × depth in inches ÷ 12 ÷ bag size.
Worked example. A 20 × 4 ft bed is 80 sq ft. At 3 in deep that’s 80 × 3 ÷ 324 = 0.74 cubic yards, or 20 cubic feet. In 2 cu ft bags that’s exactly 10 bags.
| Depth | One cubic yard covers | One 2 cu ft bag covers | One 3 cu ft bag covers |
|---|---|---|---|
| 1 in | 324 sq ft | 24 sq ft | 36 sq ft |
| 2 in | 162 sq ft | 12 sq ft | 18 sq ft |
| 3 in | 108 sq ft | 8 sq ft | 12 sq ft |
| 4 in | 81 sq ft | 6 sq ft | 9 sq ft |
How Deep Should Mulch Be?
University of Illinois Extension recommends a 2–4 in layer on well-drained sites. Finer, composted mulch works best at 2–3 in, and coarse wood chips at 3–4 in. Going deeper doesn’t help: thick layers mat down and can keep water and air away from roots.
Keep mulch at least 4 in away from tree trunks and plant stems. Mulch piled up against a trunk, often called a mulch volcano, can soften the bark and invite insects, disease, and girdling roots.
Bags or Bulk: Which Is Cheaper?
Bags are convenient for small beds. For bigger jobs, bulk usually wins once you’ve covered the delivery fee.
At $4 for a 2 cu ft bag, mulch costs $54 a cubic yard in bags (13.5 bags × $4). Bulk at $40 a yard plus $75 delivery catches up at about 5.4 cubic yards. Below that, bags are cheaper; above it, bulk is. The calculator does this math with your prices, so open the Prices section and put in what your store and local yard charge.
Two things the price comparison doesn’t show:
- Your time and your back. Five yards of mulch is about 68 two-cubic-foot bags to lift, cut open, and spread.
- Where it lands. Bulk is dumped in one pile, usually on the driveway. Plan on a wheelbarrow and a tarp.
How to Measure Your Beds
- Rectangles: measure length and width in feet.
- Round beds and tree rings: measure across the widest point for the diameter. For a ring around a tree, enter the outer and inner diameter.
- Corner beds: use the triangle shape and measure the two straight sides that meet at the corner.
- Odd shapes: break them into rectangles, circles, and triangles and add each as its own area. Being off by a few inches won’t change the order much; rounding up to whole bags covers it.
Frequently Asked Questions
How Many Bags of Mulch Are in a Cubic Yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cu ft mulch (buy 14), 9 bags of 3 cu ft, or 18 bags of 1.5 cu ft.How Much Area Does a Yard of Mulch Cover?
One cubic yard covers 324 sq ft at 1 in deep, 162 sq ft at 2 in, 108 sq ft at 3 in, and 81 sq ft at 4 in.Should I Remove Old Mulch Before Adding New?
You usually don’t need to. Top up only once the old layer has broken down, and keep the total around 2–4 in. If mulch is piled against a trunk, pull it back several inches first.How Much Does Mulch Cost?
Bagged mulch runs about $2–$8 a bag. Bulk wood mulch is about $25–$100 a cubic yard, plus $50–$150 for delivery. Prices vary a lot by region and mulch type.Sources
- Proper mulching techniques (University of Illinois Extension)
- Mulch prices (HomeGuide, updated Apr 2025)
Prices are national ballparks checked October 2026. Local prices vary.