Mulch Calculator
Mulch is sold by the cubic yard in bulk and by the bag at the store. Measure your bed, pick a depth, and this works out how much you need both ways.
Cubic yards
0.93cu yd
- Bags (2 cu ft)
- 13 bags
- Cubic feet
- 25 cu ft
Mulch for common bed sizes
Worked out with this calculator. Bag counts are rounded up to whole bags; bulk yards are not padded, so add 5–10% for uneven ground and settling.
| Area and depth | Cubic yards | 2 cu ft bags | 3 cu ft bags |
|---|---|---|---|
| 100 sq ft at 2 in | 0.62 | 9 | 6 |
| 100 sq ft at 3 in | 0.93 | 13 | 9 |
| 100 sq ft at 4 in | 1.23 | 17 | 12 |
| 200 sq ft at 2 in | 1.23 | 17 | 12 |
| 200 sq ft at 3 in | 1.85 | 25 | 17 |
| 200 sq ft at 4 in | 2.47 | 34 | 23 |
| 500 sq ft at 2 in | 3.09 | 42 | 28 |
| 500 sq ft at 3 in | 4.63 | 63 | 42 |
| 500 sq ft at 4 in | 6.17 | 84 | 56 |
How these numbers are worked out
The formula
Volume = bed area × depth. Area is length × width in feet; multiply by the depth in feet (inches ÷ 12) for cubic feet, then divide by 27 for cubic yards. Bags = cubic feet ÷ the bag's size, rounded up to whole bags.
Constants and sources
- Coverage geometry: 1 cubic yard (27 cu ft) spread 1 inch deep covers 324 sq ft. Bagged mulch volume varies by product (commonly ~2 cu ft for wood mulch) and is printed on the bag.
How it was checked
Last reviewed . Before this calculator was published, its formula, constants and worked example were checked in a separate, AI-assisted review that redid the arithmetic and tested the factual claims; the site owner then approved it for publishing. No engineer or tradesperson reviews these pages. Where a figure depends on the product (a density, a coverage rate, a bag size), it is either an input you can change above or a fixed planning value stated on this page, so check it against your product's label or your supplier.
Spot a wrong number or an outdated figure? Send a correction.
Worked example
A 10 ft × 20 ft bed at 3 inches deep: area = 200 sq ft; volume = 200 × (3 ÷ 12) = 50 cubic feet = 50 ÷ 27 ≈ 1.85 cubic yards. In 2-cubic-foot bags that's 50 ÷ 2 = 25 bags.
FAQs
- How deep should mulch be?
- 2–4 inches is the sweet spot for organic mulch: 2–3 inches to refresh an existing bed, 3–4 inches for a bare one. Going deeper doesn't just waste mulch — too-deep organic mulch traps moisture against roots (rot), harbors pests, and can turn hydrophobic and shed water instead of soaking in.
- Should mulch touch tree trunks or plant stems?
- No — keep it a few inches clear of trunks and stems. Mulch heaped against bark (a “mulch volcano”) traps moisture and invites rot, girdling roots, and disease, even though you see it done everywhere.
- How much does a cubic yard of mulch cover?
- About 324 square feet at 1 inch deep, 162 sq ft at 2 inches, or roughly 108 sq ft at 3 inches — depth and coverage trade off directly.
- Should I round up when buying mulch?
- Yes. The bag count here already rounds up to whole bags; for bulk, add about 5–10% for uneven ground and settling, and note that suppliers often sell by the whole or half cubic yard. Better a little extra than coming up short mid-bed.