One cubic yard of mulch covers roughly 100 to 150 square feet at a 3-inch depth

A cubic yard is a volume measurement: 3 feet long, 3 feet wide, and 3 feet deep. When you order mulch by the cubic yard, you are ordering that volume of material. How much ground it covers depends on how deep you spread it. At the standard landscaping depth of 3 inches, one cubic yard covers between 100 and 150 square feet. At 2 inches deep, it covers closer to 150 to 200 square feet. At 4 inches deep, it covers 75 to 100 square feet.

The range exists because mulch settles and compacts over time, and different mulch types (wood chips, shredded bark, compost blend) have different densities. Heavier, finer mulches compact more than light, chunky ones. When you first spread it, coverage is at the higher end. After a few weeks of rain and settling, it drops closer to the lower end.

Key Takeaways

  • One cubic yard of mulch at 3 inches deep covers 100 to 150 square feet, the standard depth for weed suppression and moisture retention.
  • Shallower spreading (2 inches) covers more ground but may not suppress weeds effectively; deeper spreading (4 inches) covers less but lasts longer before needing topping up.
  • Mulch settles after rain and foot traffic, so coverage shrinks by 20 to 30 percent within the first month.
  • Calculating your square footage first, then working backward to cubic yards, prevents ordering too little or too much.

How to calculate cubic yards from your garden bed size

Measure the length and width of the area you want to mulch in feet. Multiply those two numbers to get square footage. Then decide on your depth: 3 inches is standard for most beds, 2 inches for light coverage, 4 inches for heavy weed suppression or longer-lasting coverage.

Divide your square footage by the coverage rate for your chosen depth. At 3 inches, divide by 120 (the middle of the 100–150 range). At 2 inches, divide by 175. At 4 inches, divide by 87. The result is the number of cubic yards you need. For example, a 20-by-15-foot bed is 300 square feet. At 3 inches deep, 300 ÷ 120 = 2.5 cubic yards.

Round up when you get a decimal. It is better to have a small amount left over than to run short and have a thin patch. Leftover mulch keeps in a dry spot for touch-ups later in the season.

Why 3 inches is the standard depth

Three inches is deep enough to suppress most weeds and retain soil moisture through dry spells, but not so deep that it stays soggy or prevents water from reaching plant roots. Shallower mulch (1 to 2 inches) looks neat but does little to stop weeds or hold moisture. Deeper mulch (4 to 6 inches) works well for perennial beds where you do not replant every year, but it can smother shallow-rooted plants and create a barrier that keeps water from soaking in.

Around tree trunks and shrub bases, keep mulch 2 to 3 inches away from the stem itself. Mulch piled against wood promotes rot and creates habitat for pests. The goal is to cover the soil, not the plant.

How mulch settles and what to expect over time

Fresh mulch looks thick and fluffy. Within two to four weeks, rain, foot traffic, and the weight of the mulch itself compress it. You may lose 20 to 30 percent of your depth. A 3-inch layer can drop to 2 to 2.5 inches. This is normal and does not mean you ordered the wrong amount—it means the mulch is doing its job by breaking down and improving the soil.

By the end of the first growing season, mulch has settled into a stable layer. The top inch or so may have begun to decompose and darken. This is when many gardeners add a 1- to 2-inch top-up to restore the original depth and appearance. A single cubic yard of top-up mulch can refresh a 150-square-foot bed that has settled.

Mulch types and how they affect coverage

Shredded hardwood bark is the most common landscape mulch. It is medium-weight, breaks down slowly, and settles moderately. Wood chips (larger, chunkier pieces) are lighter and settle less, so they hold their depth longer. Compost-based mulch is heavier and denser, so one cubic yard covers less ground but lasts longer and enriches the soil faster.

Pine bark mulch is lighter and fluffier than hardwood, so it covers slightly more ground initially but settles faster. Dyed mulch (usually red or black) is often finer and more compact than natural mulch, so it covers less ground per cubic yard but looks uniform longer. Ask your supplier what type they stock; the difference in coverage can be 10 to 20 percent.

Common mistakes when ordering mulch

The most common error is measuring only the visible bed outline and forgetting to account for settling. If you calculate for 2.5 cubic yards based on initial coverage, order 3 cubic yards to account for compaction. Ordering too little means a thin, patchy layer that does not suppress weeds or retain moisture.

Another mistake is ordering by weight instead of volume. Mulch sold by the ton varies in density depending on moisture content and type. A ton of wet mulch is much less volume than a ton of dry mulch. Always order by cubic yards if you know your square footage, or ask the supplier to convert your square footage to cubic yards for you.

A third mistake is spreading mulch too deep around young plants. Four to six inches of mulch around a newly planted shrub can trap moisture and cause root rot. Stick to 2 to 3 inches, and keep it a few inches away from the stem.

Frequently Asked Questions

How many bags of mulch equal one cubic yard?

Most bags of mulch sold at garden centers are 2 or 3 cubic feet. One cubic yard is 27 cubic feet, so you need roughly 9 to 13 bags to equal one cubic yard, depending on bag size. Bagged mulch is more expensive per cubic yard than bulk mulch, but it is easier to transport and store if you have a small area to cover.

Does mulch weight matter when calculating coverage?

Weight does not affect coverage—volume does. One cubic yard is one cubic yard regardless of whether the mulch is wet or dry, light or heavy. Weight matters only if you are ordering by the ton instead of by volume, which is why ordering by cubic yards is clearer and more reliable.

Can I use less than 3 inches of mulch and still get weed control?

Two inches of mulch will suppress some weeds, but many perennial weeds and seeds can push through. Three inches is the minimum for reliable weed suppression. If you are short on budget or material, prioritize high-traffic or high-weed areas with 3 inches and use 2 inches in lower-priority spots.

How often do I need to add more mulch?

Top up with 1 to 2 inches of fresh mulch once a year, usually in spring or early summer. This restores depth lost to settling and decomposition. In high-traffic areas or under trees that shed a lot, you may need to top up twice a year. Mulch that has turned dark and crumbly has mostly decomposed and should be replaced.

What if my bed is an odd shape?

Break the bed into rectangles or triangles, calculate the square footage of each section, add them together, then convert to cubic yards. For a curved bed, estimate it as a rectangle that roughly matches its length and width, then subtract a percentage for the curves. Overestimating slightly is safer than underestimating.