How much mulch do I need?
Mulch is sold two ways — by the bag and by the cubic yard — and the amount you need comes down to two numbers: the area of your beds and how deep you spread it. Here's how to get both right so you order once.
Start with depth, not area
Most people measure their beds first, but depth is what trips up the order. For most landscape beds, a 2–3 inch layer of mulch is the standard recommendation — enough to suppress weeds and hold moisture without smothering roots. Use the thinner end for fine, shredded mulch and the thicker end for coarse bark nuggets.
Around trees, keep mulch 2–4 inches deep and pull it back from the trunk — never pile it against the bark in a cone (the "mulch volcano" that traps moisture and invites rot). Topping up an existing bed usually only needs 1–2 inches to refresh the color and depth.
Depth quick-reference by situation
| Situation | Recommended depth | Notes |
|---|---|---|
| New landscape bed | 3 in | Weed suppression is the priority; 3 in reliably blocks light |
| Topping up existing bed | 1–2 in | Add only what's needed to bring total depth back to 3 in |
| Around trees | 2–4 in | Keep 3–6 in clear of trunk; no mulch volcanoes |
| Fine-textured shredded mulch | 2 in | Fine mulch compacts; thicker layers can shed water |
| Coarse bark nuggets | 3 in | Larger pieces let light through at shallow depths |
| Vegetable garden paths | 4 in | Extra depth handles foot traffic compression |
Turn area + depth into cubic yards
Mulch volume is just area × depth. Measure each bed's length and width in feet and multiply for the square footage; split L-shapes and curves into rectangles and add them up. Then convert depth from inches to feet and divide by 27 (the number of cubic feet in a cubic yard):
cubic yards = (square feet × depth-in-inches ÷ 12) ÷ 27
For example, a 200 sq ft bed at 3 inches deep is
(200 × 0.25) ÷ 27 = 1.85 cubic yards — round up to 2.
A useful shortcut: 1 cubic yard at 3 inches deep covers 108 square feet
(because 27 × 4 = 108; 3 inches is a quarter of a foot). At 2 inches
deep, that same yard covers 162 square feet. Keep those numbers handy when estimating —
they let you do most jobs in your head.
Worked example: three front-yard beds
You have three beds to mulch fresh this spring:
- Foundation bed: 4 ft × 30 ft = 120 sq ft
- Corner bed: 8 ft × 10 ft = 80 sq ft
- Tree ring (approximate circle, radius 4 ft): about 50 sq ft
Total area: 120 + 80 + 50 = 250 sq ft. You want 3 inches on the
new beds and 2 inches on the tree ring. For simplicity, split the job:
- Foundation + corner beds at 3 in:
(200 × 0.25) ÷ 27 = 1.85 cu yd - Tree ring at 2 in:
(50 × 0.167) ÷ 27 = 0.31 cu yd - Total:
1.85 + 0.31 = 2.16 cu yd— order 2.5 yards to cover settling and irregular bed edges
At 2.5 yards, bulk delivery makes clear sense. Use the Landscape Material Calculator to get the exact figure and a bag count comparison before you call the supplier.
Bags or bulk?
Bagged mulch is graded by cubic feet. The most common bag is 2 cubic feet, which covers about 12 square feet at 2 inches deep (or 8 square feet at 3 inches). Since a cubic yard is 27 cubic feet, it takes about 13–14 of those 2 cu ft bags to equal one bulk yard.
When comparing prices, divide the bag price by the bag's cubic footage to get cost per cubic foot, then multiply by 27 to get the cost-per-yard equivalent. This lets you compare apples to apples with a bulk quote. Typical bulk hardwood mulch runs $25–$55 per yard delivered; the bagged equivalent at $5–$7 per 2 cu ft bag works out to $68–$95 per yard-equivalent — so bulk is almost always the better deal once you're ordering more than a yard. Regional prices vary; always check locally.
Always round up
Beds are never perfectly flat and mulch settles, so order a little extra rather than coming up a half-bag short. The calculator rounds bag counts up automatically and shows both the cubic-yard and bag figures so you can compare bulk and bagged pricing at your supplier. If you're filling a raised bed with soil rather than top-dressing with mulch, the Raised Bed Soil Calculator handles that volume separately.
Common mistakes
- Applying too deep. More than 4 inches of mulch can prevent rain from reaching the soil, create anaerobic conditions that suffocate shallow roots, and become a habitat for rodents. Stick to 2–3 inches for beds; 4 inches maximum for paths.
- The mulch volcano. Piling mulch against a tree trunk — even 2–3 inches of it touching the bark — traps moisture and promotes fungal rot and pest damage. Pull it back so there's bare soil for 3–6 inches around the trunk.
- Skipping the weed barrier question. Landscape fabric under mulch can reduce long-term maintenance in stable ornamental beds, but it inhibits soil biology and causes problems in beds you plan to replant. If you use it, factor the fabric into the project before you calculate mulch depth.
- Forgetting that topping up is cheaper than starting fresh. An existing bed that has settled to 1 inch only needs 1–2 inches of new mulch, not a full 3-inch application. Measure the current depth before you order.