A yard of mulch covers 324 square feet at 1 inch deep
One cubic yard of mulch — the standard unit sold at garden centers — covers 324 square feet when spread 1 inch thick. This is the most common depth for mulch around plants and garden beds. If you spread it 2 inches thick, the same yard covers 162 square feet. At 3 inches, it covers 108 square feet. The thicker you lay it, the fewer square feet one yard will cover.
The math is straightforward: a cubic yard is 27 cubic feet. Divide 27 by the depth in feet, and you get your square footage. For 1 inch (which is 1/12 of a foot), the calculation is 27 ÷ (1/12) = 324 square feet. Most landscapers recommend 2 to 3 inches for weed suppression and moisture retention, so plan on one yard covering between 108 and 162 square feet depending on how deep you want to go.
Key Takeaways
- One cubic yard of mulch covers 324 square feet at 1 inch deep, 162 square feet at 2 inches deep, and 108 square feet at 3 inches deep.
- Depth matters more than the type of mulch — wood chips, bark, or shredded hardwood all follow the same coverage math.
- To find how many yards you need, measure your bed in square feet, decide on your depth, and divide accordingly.
- Mulch settles and breaks down over time, so ordering 10 to 15 percent extra accounts for settling in the first few weeks.
How to calculate the yards you need
Start by measuring the length and width of your bed in feet, then multiply them together to get square footage. If your bed is 10 feet long and 4 feet wide, that is 40 square feet. Next, decide on your depth. Two inches is the standard for most planting beds because it suppresses weeds without piling mulch against tree trunks or plant stems.
Once you know your square footage and depth, use this table to find how many yards to order:
| Square Feet | 1 Inch Deep | 2 Inches Deep | 3 Inches Deep |
|---|---|---|---|
| 100 sq ft | 0.3 yards | 0.6 yards | 0.9 yards |
| 200 sq ft | 0.6 yards | 1.2 yards | 1.9 yards |
| 300 sq ft | 0.9 yards | 1.9 yards | 2.8 yards |
| 400 sq ft | 1.2 yards | 2.5 yards | 3.7 yards |
| 500 sq ft | 1.5 yards | 3.1 yards | 4.6 yards |
If your bed is an irregular shape, break it into rectangles, calculate each one, and add them together. A bed that is 10 feet long, 4 feet wide at one end, and 6 feet wide at the other is easier to think of as two rectangles: one 10 by 4 (40 square feet) and one 10 by 2 (20 square feet), for a total of 60 square feet.
Why depth matters for mulch performance
Mulch at 1 inch thick does little to stop weeds or hold moisture. At that depth, sunlight still reaches the soil, and water evaporates quickly. One inch is useful only as a top dressing over existing mulch or when you are refreshing a bed that already has a base layer underneath.
Two inches is the practical minimum for new beds. It blocks most light from reaching weed seeds, keeps soil cooler in summer, and reduces water loss. Three inches offers better weed suppression and moisture retention but risks piling mulch against tree trunks and plant stems, which can trap moisture and cause rot. Never mound mulch against the base of a tree or shrub — keep it 3 to 4 inches away from the stem.
Accounting for settling and breakdown
Fresh mulch settles within the first few weeks as it absorbs water and the pieces compress. You may lose 10 to 15 percent of your depth in that time. If you want to maintain 2 inches after settling, order enough for 2.3 inches initially. This is why many landscapers recommend ordering slightly more than the calculator suggests.
Mulch also breaks down over time. Wood-based mulches last 1 to 2 years before they begin to decompose noticeably. Bark mulch lasts slightly longer. As it breaks down, it enriches the soil but becomes thinner, so you will need to top it off annually or every other year depending on the type and your climate. Hot, wet climates speed decomposition; cool, dry climates slow it.
Different mulch types and coverage
The coverage calculation — 324 square feet per yard at 1 inch — applies to all mulch types: shredded hardwood, wood chips, bark nuggets, and recycled wood. The type you choose affects color, longevity, and how quickly it breaks down, but not how many square feet one yard covers.
Dyed mulch (usually black or red) lasts slightly longer than natural wood mulch because the dye slows decomposition. Bark nuggets are larger pieces and may settle less than shredded mulch, but the difference is small enough that you should still plan for 10 to 15 percent settling. Recycled wood mulch is often cheaper and covers the same area as new mulch.
Common mistakes when ordering mulch
The most common error is underestimating depth. Many people think 1 inch will work and end up with a thin layer that does not suppress weeds. Order for 2 inches minimum unless you are topping off an existing bed that already has depth underneath.
Another mistake is not accounting for settling. If you measure your bed, calculate the yards needed, and order exactly that amount, you will have noticeably less mulch after two weeks. Add 10 to 15 percent to your order to end up where you want to be.
A third error is piling mulch against tree trunks and plant stems. This traps moisture and can cause root rot and pest damage. Keep mulch 3 to 4 inches away from any stem, even if it means your bed looks a little thin near the base of the tree.
Frequently Asked Questions
Does mulch type change how many square feet it covers?
No. One cubic yard of any mulch type — wood chips, bark, shredded hardwood, or recycled wood — covers 324 square feet at 1 inch deep. The type affects color, how long it lasts, and how quickly it breaks down, but not the coverage area.
How much mulch do I need for a 10 by 10 foot bed?
A 10 by 10 foot bed is 100 square feet. At 2 inches deep, you need 0.6 cubic yards. At 3 inches deep, you need 0.9 cubic yards. Most garden centers sell mulch by the yard, so you would order 1 yard and have some left over, or ask if they sell half-yards.
Should I use 2 inches or 3 inches of mulch?
Two inches is the standard for most planting beds because it suppresses weeds and retains moisture without piling mulch against plant stems. Use 3 inches only if your bed is large enough to keep mulch 3 to 4 inches away from all tree trunks and shrub stems. Never go deeper than 3 inches.
How often do I need to add more mulch?
Mulch breaks down over 1 to 2 years depending on the type and climate. Top it off annually or every other year to maintain depth. You typically need much less mulch for refreshing than for the initial process — often just 0.5 to 1 inch added on top of what remains.
Can I use mulch that is been sitting in a pile for months?
Yes. Mulch that has been stored will have settled and may be slightly decomposed, but it still covers the same area per cubic yard. It may settle less after installation because it has already compressed, which is actually an advantage — you lose less depth in the first few weeks.