How Much Mulch Do I Need? (Cubic Yards to Bags)
Quick answer: length × width × depth (in feet) ÷ 27 = cubic yards. A 10×20 ft bed at 3 in deep needs about 1.85 cubic yards — roughly 25 bags of 2 cu ft mulch. Here's the full method.
- Mulch volume formula
- Depth by use
- Cubic yards to bags
- Worked example
- Ordering tips
- Common mistakes
Mulch volume formula
Mulch is sold by volume: bulk by the cubic yard, bags by cubic feet (usually 2 cu ft). Work in feet:
Length (ft) × Width (ft) × Depth (ft) ÷ 27 = cubic yards. Convert depth from inches first: 3 in = 0.25 ft, 2 in = 0.167 ft.
Depth by use
| Purpose | Recommended depth |
|---|---|
| Around established plants | 2 in |
| Flower beds / new plants | 3 in |
| Weed suppression | 3–4 in |
| Play areas / walkways | 4–6 in |
Cubic yards to bags
One cubic yard = 27 cubic feet. Common bag sizes: 2 cu ft bag → about 14 bags per yard; a 3 cu ft bag → about 9 bags per yard. Bulk by the yard is usually cheaper than bags for big beds.
Worked example
- Bed = 10 × 20 = 200 sq ft
- Depth = 3 in = 0.25 ft
- Volume = 200 × 0.25 = 50 cu ft
- Cubic yards = 50 ÷ 27 = 1.85 cu yd
- 2 cu ft bags = 50 ÷ 2 = 25 bags
Ordering tips
For beds under ~2 cubic yards, bags are convenient — you can bring them home in a car. For anything bigger, order bulk and have it dumped; it's cheaper per yard. Wood mulch settles, so a 2–3 in layer is usually enough; don't pile it against tree trunks (bark rot).
Quick lookup: common bed sizes
Here's what common planting beds need at a 3-inch depth:
| Bed size | Volume | Cubic yards | 2 cu ft bags |
|---|---|---|---|
| 4×8 ft (small) | 8 cu ft | 0.3 | ~4 |
| 10×10 ft | 25 cu ft | 0.9 | ~13 |
| 10×20 ft | 50 cu ft | 1.9 | ~25 |
| 20×20 ft | 100 cu ft | 3.7 | ~50 |
| 50×10 ft border | 125 cu ft | 4.6 | ~63 (order bulk) |
Mulch types & what they cost
Mulch type affects price and function. Hardwood bark is the common, affordable choice. Shredded bark holds moisture well and stays put on slopes. Cedar is light, aromatic, and pest-repellent but pricier. Rubber mulch lasts years (often in play areas) but is heavier and costlier. Bagged mulch runs roughly $3–$6 per 2 cu ft bag; bulk by the cubic yard is typically $30–$60 per yard delivered, usually cheaper per square foot for big beds.
Bulk vs bagged: which saves more
For small beds, bags are fine. Once you need more than about 2 cubic yards, bulk wins: it's cheaper per yard and you don't haul dozens of bags. Order slightly over and spread it out — mulch compacts and settles, so a little extra tops up thin spots. Skip the colored rubber mulch near vegetable gardens, and keep organic mulch a few inches clear of tree trunks.
FAQ
At a 3-inch depth, 100 sq ft needs 25 cubic feet — about 13 bags of 2 cu ft mulch, or roughly 0.93 cubic yards. Adjust for your depth: shallower uses less, deeper more.
One cubic yard (27 cu ft) covers 108 square feet at 3 inches deep, 162 sq ft at 2 inches, and 81 sq ft at 4 inches. Divide your area by these numbers for the yards you need.
Bulk by the cubic yard is usually cheaper for beds over about 2 yards. Bags are more convenient for small beds and let you carry it home, but cost more per cubic foot.
About 2 inches around established plants, 3 inches for new flower beds, and 3–4 inches for weed suppression. More than 4 inches can smother roots and trap too much moisture.
Common mistakes
- Forgetting to convert inches to feet. 3 inches written as "3 ft" over-orders by 12×.
- Piling too deep. Over 4 in can smother roots and trap moisture.
- Ignoring bag size. 2 cu ft and 3 cu ft bags differ — check before buying.
- Not accounting for odd shapes. Split curved beds into rectangles and add them.