How to use the mulch calculator
- Measure each bed. Use length and width in feet for rectangular beds, or the diameter for a ring around a tree. If several beds are the same size, enter one and set the number of beds.
- Choose a depth. Three inches is right for most beds. See the depth guide below.
- Pick your bag size. Most bagged mulch comes in 2 cubic foot bags. The calculator rounds up to whole bags.
- Compare prices. Enter a bag price and a bulk price with delivery to see which is cheaper for your job.
Mulch formula
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size (cu ft), rounded up
One cubic yard of mulch covers about 324 square feet at 1 inch deep, 162 square feet at 2 inches, and 108 square feet at 3 inches.
How deep should mulch be?
| Use | Depth |
|---|---|
| Topping up existing mulch | 1 to 2 in |
| Flower beds and borders | 2 to 3 in |
| Shrubs and tree rings | 3 to 4 in |
| Weed suppression on bare ground | 3 to 4 in |
| Playground (wood chips) | 9 to 12 in |
Keep mulch 2 to 3 inches away from tree trunks and plant stems. Piling it against the bark (the so-called mulch volcano) traps moisture and invites rot and pests.
Worked examples
A 20 × 4 ft front border at 3 inches
20 × 4 = 80 square feet. 80 × 3 ÷ 12 = 20 cubic feet, which is 10 bags of 2 cu ft or 0.74 cubic yards.
Five tree rings, 6 ft across, 3 inches deep
Each ring is 3.1416 × 3 × 3 = 28.3 square feet. Five rings are 141.4 square feet. At 3 inches that is 35.3 cubic feet, so 18 bags of 2 cu ft, or about 1.3 cubic yards.
Bags or bulk?
A cubic yard equals 13.5 bags of 2 cubic feet. If bags cost $4 each, a yard of bagged mulch costs about $54, while bulk mulch is often $30 to $50 per yard plus delivery. For small jobs under 1 to 2 yards, bags are simpler. For whole-yard projects, bulk usually wins, even after the delivery fee.
Choosing a mulch
- Shredded hardwood: knits together and stays put on slopes. Breaks down in 1 to 2 years and feeds the soil.
- Pine bark nuggets: long lasting and attractive, but light pieces can float away in heavy rain.
- Pine straw: cheap and light, good for acid-loving plants. Sold by the bale; one bale covers about 50 square feet.
- Rubber mulch: does not decompose and is common in playgrounds, but adds nothing to the soil.
- Stone: permanent and good near the house, but heats up in sun. Use the gravel calculator for stone.
Frequently asked questions
How many bags of mulch are in a yard?
One cubic yard equals 27 cubic feet, so it takes 13.5 bags of 2 cubic feet, 9 bags of 3 cubic feet, or 18 bags of 1.5 cubic feet.
How much area does a bag of mulch cover?
A 2 cubic foot bag covers 12 square feet at 2 inches deep, 8 square feet at 3 inches, or 24 square feet at 1 inch.
How much mulch do I need for 100 square feet?
At 3 inches deep you need 25 cubic feet, which is about 0.93 cubic yards or 13 bags of 2 cubic feet.
How deep should mulch be?
Two to three inches for flower beds, three to four inches for shrubs and trees. More than about four inches can suffocate roots.
Is it cheaper to buy mulch in bulk?
Usually, once you need more than one or two cubic yards. Bulk mulch often costs less than bagged even after a delivery fee. Enter both prices in the calculator above to compare.
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Last updated October 2026.