One yard of mulch covers roughly 100 to 150 square feet at a 3-inch depth
A cubic yard of mulch—the standard unit sold at garden centers and landscape suppliers—spreads across about 100 to 150 square feet when laid 3 inches deep. That 3-inch depth is the industry standard for weed suppression and moisture retention. If you spread it thinner (2 inches), one yard covers closer to 150 to 160 square feet. If you go deeper (4 inches), it covers only 75 to 100 square feet. The exact coverage depends on how densely you pack it and how level your ground is.
The math is straightforward: a cubic yard contains 27 cubic feet. Spread across a bed 3 inches deep (which is 0.25 feet), that divides into roughly 108 square feet of coverage. In practice, mulch settles and compacts slightly after you lay it, and you lose a bit to uneven ground, so most people plan for 100 to 110 square feet per yard as a working number.
Key Takeaways
- One yard of mulch at 3 inches deep covers approximately 100 to 150 square feet, depending on how tightly you pack it.
- Shallower mulch (2 inches) stretches further but provides less weed control; deeper mulch (4 inches) covers less ground but lasts longer before needing topping off.
- Measure your bed length and width in feet, multiply them together, then divide by 100 to get a rough yard count.
- Mulch settles over time, so plan to add a thin layer every year or two to maintain the 3-inch depth.
How to calculate the yards you need
Start by measuring the length and width of each bed in feet. Multiply length by width to get square footage. If your bed is 10 feet long and 4 feet wide, that is 40 square feet. Divide that number by 100 (using the conservative estimate for 3-inch depth), and you get 0.4 yards—so you would order 1 yard to have extra.
For irregularly shaped beds, break them into rectangles. A bed shaped like an L can be split into two rectangles, measured separately, then added together. If you have a circular bed, measure the radius (the distance from the center to the edge), multiply it by itself, then multiply by 3.14, and divide by 100.
Always round up. It is better to have a small pile left over than to run short and have to make a second trip or leave part of a bed uncovered.
Why depth matters more than you might think
The 3-inch standard exists because it is the minimum depth needed to suppress most weeds and retain soil moisture through dry spells. At 2 inches, mulch still helps, but weeds are more likely to push through, especially if the mulch is coarse or loosely laid. At 4 inches or deeper, you get better weed control and longer-lasting moisture retention, but you also use more material and may trap too much moisture against the soil in very wet climates, which can encourage rot in plant stems.
Mulch also breaks down over time—typically losing 20 to 30 percent of its volume in the first year as it decomposes and settles. That is actually good for your soil, but it means a bed that starts at 3 inches may drop to 2 inches by midsummer. Many gardeners plan to add a 1-inch top-off layer every spring or every other spring to maintain coverage.
Different mulch types cover different areas
The coverage numbers above assume standard wood chip or bark mulch, which is what most people buy. Shredded hardwood mulch, which is finer and denser, may cover slightly less ground per yard because it compacts more tightly. Straw or hay mulch, which is much lighter and fluffier, may appear to cover more ground initially but settles dramatically and breaks down faster.
Rubber mulch and colored mulch (dyed wood chips) behave similarly to standard wood mulch in terms of coverage, though rubber mulch lasts much longer and does not break down. Compost-based mulches are heavier and denser, so one yard covers less area but enriches the soil as it breaks down.
If you are using a specialty mulch, ask the supplier for their coverage estimate—they often have tested their specific product and can give you a more precise number than the general 100-to-150 range.
How to spread mulch evenly
Dump the mulch in piles around the bed rather than in one central pile. Use a shovel or mulch fork to spread it, working from the piles outward. Rake it level as you go. The goal is a consistent depth across the entire bed, not a volcano shape with mulch piled high around plant stems.
Keep mulch 3 to 4 inches away from tree trunks and plant stems. Mulch piled against wood or bark can trap moisture and cause rot or encourage insects and disease. A small ring of bare soil around the base of each plant prevents this problem.
Accounting for plants already in the bed
When you measure your bed, measure the entire bed area, not the space between plants. You will need mulch to cover the whole surface. However, you do not need to mulch directly over the crown (the base where stems meet roots) of perennials or shrubs, so you will use slightly less than your calculation suggests—usually 5 to 10 percent less, depending on how densely planted the bed is.
For a heavily planted bed with many shrubs or perennials, you might subtract 10 to 15 percent from your yard count. For a bed with just a few plants, subtract nothing—the mulch around them is what matters most.
When to buy mulch and what to expect
Mulch is cheapest in spring (March through May) when demand is highest and suppliers have fresh stock. Summer and fall prices are often higher. Bagged mulch costs more per cubic yard than bulk mulch delivered by truck, but it is easier to handle if you have a small bed or no way to receive a delivery.
If you order bulk mulch, ask the supplier whether they charge by the yard or by weight, and whether delivery is included. A cubic yard of wet mulch (freshly ground) weighs more than dry mulch, so some suppliers measure by weight rather than volume. Get a clear quote before ordering.
Frequently Asked Questions
Can I use less than 3 inches of mulch?
Yes, but it is less effective. Two inches still suppresses some weeds and retains some moisture, but you will see more weeds poking through, especially in hot or dry weather. One inch is mostly decorative and provides little practical benefit.
How often do I need to add more mulch?
Most mulch needs a 1-inch top-off layer every one to two years, depending on how fast it breaks down in your climate. Hotter, wetter climates break mulch down faster. Rubber mulch lasts 8 to 10 years before needing replacement.
What if my bed is very uneven or sloped?
Measure the average depth you want and calculate based on that. On a slope, mulch will migrate downhill over time, so you may need to rake it back up or add extra mulch to the upper part of the bed. Landscape fabric pinned under the mulch can slow migration.
Is there a difference between mulch coverage in sun versus shade?
No—the coverage calculation is the same. However, mulch in shade breaks down more slowly because it stays cooler and damper, so you may not need to top it off as often. Mulch in full sun breaks down faster and may need refreshing more frequently.
Can I mix different types of mulch in one bed?
Yes. You might use a finer mulch near plants and coarser mulch in open areas, or layer compost under wood mulch for soil enrichment. Just measure the total area and calculate the total yards needed, accounting for the depth of each layer.