Worked example: mulch for an 18 × 4 ft bed
Hypothetical educational example of one rectangular bed. It is not a planting plan. The 2 cubic foot bag is a size the calculator offers. Scotts lists a 2 cu ft mulch bag; this example does not claim a particular color or coverage beyond that volume.
Inputs
| Bed | 18 × 4 ft |
|---|---|
| Depth | 3 in |
| Settling extra | 0% |
| Bag | 2 cu ft |
Arithmetic
- Area = 72 sq ft.
- Volume = 72 × 3 ÷ 12 = 18 cu ft = 18 ÷ 27 = 0.667 cu yd, displayed as 0.67 cu yd.
- Bags = 18 ÷ 2 = 9 exactly.
Required, waste and purchase
- Required
- 18 cu ft, which is 0.67 cu yd.
- Purchased
- 9 × 2 cu ft bags. Because the volume divides evenly, requirement and purchase are the same. No extra bag is added for settling, because that field is 0 in this example.
- Units
- US feet, inches, cubic yards and 2 cu ft bags. One cubic yard is 27 cubic feet.
Assumptions
- A 2 cu ft bag is a retail size, including one Scotts lists. It is not every mulch bag.
- Depth of 3 inches sits inside the 2 to 4 inch range Iowa State University Extension describes for many hardwood mulches. It is not a required depth for every bed.
What this example does not decide
- No fabric, edging or plant counts.
- Topsoil under the mulch is a different calculator and is not inside the 9 bags.
Where to go next
- Mulch calculator — Run these inputs
- Loose materials topic — Area × depth
- Depth guide — How deep each loose material is placed
- Topsoil calculator — Soil under a new bed, if you need it
Questions
Why is there no tenth bag?
18 cubic feet divided by 2 is 9. The settling field is 0, so nothing is added before the division. Turn settling on if you want extra depth after the mulch compresses.
Is this a whole garden design?
No. It is one rectangular bed. Paths, gravel and soil are other calculators.
Sources
- Iowa State University Extension – mulch depth — accessed 2026-10-20: “Many hardwood chipped or shredded mulches are spread between 2 and 4 inches thick.”
- Scotts – Nature Scapes Color Enhanced Mulch — accessed 2026-10-20: “Nature Scapes Color Enhanced Mulch 2 cu. ft.”