Which volume unit for which job
Match the unit to the job size. The conversions are mechanical (27 cu ft = 1 cu yd, 1 cu ft ≈ 28.3 L), but the right reporting unit depends on how mulch will be delivered and counted.
| Job size | Best unit to order in | Why | Typical buy |
|---|---|---|---|
| Under 6 cu ft | Cubic feet (bags) | Below bulk minimum, sold by bag | 2–3 bags of 2 cu ft |
| 6–25 cu ft | Cubic feet (bags) | Bulk delivery fee eats savings | 3–13 bags |
| 25–80 cu ft | Cubic yards | Crosses bulk break-even at ~3 cu yd | 1–3 cu yd bulk |
| 80+ cu ft | Cubic yards | Free-delivery threshold reached | 3+ cu yd bulk |
| Metric / EU job | Liters | Pallets ship in 50/70/80 L bags | 10–30 metric bags |
| Container / pot | Liters or quarts | Potting mulch sold by liter | 10–50 L bags |
The settling buffer most calculators skip
Organic mulch settles 15–20% in the first 30 days. That's why our calculator and most extension services recommend adding a 10% buffer to the raw volume — it leaves you with the depth you actually wanted after settling, not the depth you measured on installation day.
USDA Forest Service field studies indicate that organic mulch volume can decrease by 15–25% in the first season due to settling and microbial decomposition, supporting the common 10% over-order buffer recommended by landscape practitioners.
The unit conversions you'll need on receipt day
- 1 cubic yard = 27 cubic feet. Memorize this; everything else follows.
- 1 cubic yard ≈ 765 liters ≈ 0.765 cubic meters. Useful when comparing US bulk to metric pallets.
- 1 cubic foot ≈ 28.3 liters ≈ 7.48 US gallons. The bag-to-watering-can conversion.
- 1 cubic meter ≈ 1.31 cubic yards ≈ 35.3 cubic feet. Standard European bulk unit.
- 13.5 bags of 2 cu ft = 1 cubic yard. The shopping-cart conversion.
- 9 bags of 3 cu ft = 1 cubic yard. Cleanest math; what landscapers prefer.
Worked example: a 200 sq ft mixed bed
Why depth matters as much as area
Two beds with the same volume can have radically different footprints. A 100 sq ft bed at 3 in depth is 25 cu ft — exactly the same mulch order as a 50 sq ft bed at 6 in depth. Your supplier doesn't care how the volume was distributed; they ship volume.
Practical implication: when you have leftover mulch from a previous job, you can spread it deeper on a smaller bed rather than driving back for a fresh load. Cornell Bulletin 245 caps organic mulch at 4 inches over established root zones — beyond that, oxygen exchange to the roots drops noticeably.