How Much Mulch Do I Need? Coverage Chart & Bulk vs Bags

Mulch is one of the easiest materials to over- or under-buy, because it is sold by volume (cubic yards or cubic feet) but you measure your beds by area. The bridge between the two is depth, and once you understand that, the math takes a minute. One cubic yard of mulch covers about 108 square feet at 3 inches deep.

How much area does a cubic yard of mulch cover?

A cubic yard is 27 cubic feet. Spread across a flat bed, the thinner the layer, the more area it covers:

The number of bags per cubic yard does not change with depth. A 2 cubic foot bag is always 1/13.5 of a yard, but the area each bag covers does. A 2 ft³ bag covers 12 ft² at 2 inches deep, and 8 ft² at 3 inches.

The formula

1. Measure the area of the bed in square feet. For a rectangle, multiply length by width. For a curved bed, break it into simple shapes, or use the area calculator.
2. Choose a depth in inches and divide by 12 to convert it to feet.
3. Multiply: cubic feet = area × depth in feet.
4. Divide by 27 for cubic yards, or by 2 or 3 for the number of bags.

For example, a 200 ft² bed at 3 inches deep: 200 × 0.25 = 50 ft³. That is 1.85 cubic yards, 25 bags of 2 ft³, or 17 bags of 3 ft³.

Mulch needed by bed size

Cubic yards of mulch for common bed areas:

How deep should mulch be?

For most flower beds, shrub borders and vegetable paths, 2 to 3 inches is the sweet spot. It is thick enough to block most weeds and hold moisture, but thin enough for water and air to reach the roots.

• Too thin (under 2 inches) lets sunlight through, so weeds germinate.
• Too thick (over 4 inches) can hold too much moisture, starve roots of oxygen and shelter pests. Fine mulches like shredded bark mat down and shed water if you pile them deep.
• Coarse mulch (chunks, nuggets, large chips) can go a little thicker since it lets air through.
• Existing mulch: before adding a new layer, check what is there. Mulch breaks down and settles, so a bed may only need an inch to top it up, or a rake to fluff it up.

Keep mulch a few inches away from tree trunks and the stems of shrubs. Mulch piled against bark traps moisture and encourages rot, which is why the "mulch volcano" is a classic landscaping mistake.

Bulk or bagged mulch?

Bagged mulch is easy to buy, carry and store, and you can pick up just what you need. But per cubic foot it costs considerably more than bulk. As a rule:

• Under about 1 cubic yard (roughly 14 bags): bags are usually fine. The delivery fee and minimum on bulk will wipe out the saving.
• 2 cubic yards and up: bulk is usually cheaper, often by a large margin, and a single delivery saves a lot of trips. Check the delivery fee, which varies by distance.
• Pickup truck: most suppliers will load a yard or two into a pickup. Mulch is light, so a full-size truck bed can often handle 2 yards, but wet mulch weighs more.

The mulch calculator compares bulk and bagged costs at your local prices.

Choosing a mulch

• Shredded hardwood or bark: knits together, stays put on slopes, and breaks down slowly. A reliable general-purpose choice.
• Wood chips (arborist chips): often free or very cheap from tree services. Good for paths and around trees. They may be coarse and mixed.
• Pine straw: light, easy to spread and good on slopes. It acidifies the soil only slightly, if at all.
• Compost or leaf mold: feeds the soil and suits vegetable gardens. It does not suppress weeds as well as coarse mulch.
• Stone and rubber: long-lasting but do not feed the soil. Stone gets hot in full sun. Both are better around patios and play areas than around plants.

Tips for a better result

• Edge the bed first. A clean edge holds mulch in and gives a tidy line.
• Weed before mulching, or lay cardboard or a layer of landscape fabric underneath for stubborn weeds.
• Water the bed, then mulch. Wet soil under the mulch holds the moisture.
• Refresh every year or two, by adding only an inch or so on top.