How Much Mulch Do I Need?
Short answer: 100 square feet of garden bed at 3 inches deep takes 25 cubic feet of mulch, which is about 0.93 cubic yards or 13 bags of 2 cubic feet. One cubic yard covers about 108 square feet at 3 inches.
How deep should mulch be?
- 2 inches: topping up existing beds, vegetable gardens and fine mulches.
- 3 inches: the usual choice for new beds and around shrubs. It blocks most weeds and holds moisture.
- 4 inches: coarse bark in areas with heavy weeds, paths and play areas. Deeper than about 4 inches can keep air and water from reaching roots.
Keep mulch a few inches away from tree trunks and plant stems. A "volcano" piled against the bark traps moisture and invites rot and pests.
The formula
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size (usually 2 cu ft), rounded up
Mulch per 100 square feet
| Depth | Cubic feet | Cubic yards | 2 cu ft bags | One cubic yard covers |
|---|---|---|---|---|
| 2 in | 16.7 | 0.62 | 9 | 162 sq ft |
| 3 in | 25 | 0.93 | 13 | 108 sq ft |
| 4 in | 33.3 | 1.23 | 17 | 81 sq ft |
Mulch for common bed sizes at 3 inches
| Area | Cubic yards | 2 cu ft bags |
|---|---|---|
| 50 sq ft | 0.46 | 7 |
| 100 sq ft | 0.93 | 13 |
| 200 sq ft | 1.85 | 25 |
| 500 sq ft | 4.63 | 63 |
| 1,000 sq ft | 9.26 | 125 |
How much mulch is in a bag and in a yard?
Most bagged mulch at garden centers comes in 2 cubic foot bags; some are 1.5 or 3 cubic feet. A cubic yard is 27 cubic feet, so one yard equals 13.5 bags of 2 cubic feet. That makes the math for "bags or bulk?" simple: if a 2 cu ft bag costs $4, a yard's worth of bags is $54. Compare that with the bulk price per yard plus delivery.
As a rule, once you need around 3 cubic yards or more, bulk delivery is usually cheaper and creates far less plastic waste. Bags win for small beds, tight access and when you want to spread the work over several weekends.
Worked example
You have two beds: one is 20 × 4 ft and the other is a circle 8 ft across around a tree. You want 3 inches.
- Rectangle: 20 × 4 = 80 sq ft.
- Circle: 3.14 × 4 × 4 = 50.3 sq ft.
- Total: 130.3 sq ft × 3 ÷ 12 = 32.6 cubic feet, or 1.21 cubic yards.
- In 2 cubic foot bags: 32.6 ÷ 2 = 16.3, so 17 bags.
Tips that save money
- Measure the beds, not the yard. Estimating by eye usually overshoots by a third.
- Top up, do not replace. Last year's mulch breaks down but still counts. Rake it, then add 1 to 2 inches.
- Lay landscape fabric or cardboard under new beds to cut weeds without going deeper.
- Ask about free arborist chips. Tree services often give away chipped wood, which works well on paths.
Filling new beds before you mulch? Work out soil with the topsoil calculator. Using stone instead of bark? Use the gravel calculator.
Try the mulch calculator
Enter your own numbers below, or open the full mulch calculator with the formula and more examples.
Frequently asked questions
How much mulch do I need for 100 square feet?
At 3 inches deep, 25 cubic feet: about 0.93 cubic yards or 13 bags of 2 cubic feet. At 2 inches it is about 9 bags.
How many bags of mulch are in a yard?
13.5 bags of 2 cubic feet, 9 bags of 3 cubic feet or 18 bags of 1.5 cubic feet.
How many square feet does a yard of mulch cover?
About 162 sq ft at 2 inches deep, 108 sq ft at 3 inches and 81 sq ft at 4 inches.
How deep should mulch be to prevent weeds?
About 3 inches for most beds. Coarse bark up to 4 inches works for heavy weed areas; deeper can harm plant roots.