Mulch Calculator
Enter the size of your garden bed and how deep you want the mulch. You'll get the volume in cubic yards, how many bags to buy, and whether bulk delivery is cheaper.
Mulch formula
Cubic feet = length (ft) × width (ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size (2 or 3 cu ft)
Example
A 20 × 4 ft bed is 80 sq ft. At 3 inches deep that is 80 × 3 ÷ 12 = 20 cu ft, or 0.74 cubic yards. You need 10 bags of 2 cu ft mulch.
How deep should mulch be?
| Use | Depth |
|---|---|
| Top-up of existing mulch | 1 in (2.5 cm) |
| Flower and shrub beds | 2–3 in (5–7.5 cm) |
| Weed control, paths | 3–4 in (7.5–10 cm) |
Keep mulch a few inches away from tree trunks and plant stems — “mulch volcanoes” piled against trunks trap moisture and invite rot and pests.
One cubic yard of mulch covers…
- 324 sq ft at 1 inch deep
- 162 sq ft at 2 inches
- 108 sq ft at 3 inches
- 81 sq ft at 4 inches
Frequently asked questions
How many bags of mulch are in a yard?
One cubic yard is 27 cubic feet: about 13.5 bags of 2 cu ft or 9 bags of 3 cu ft.
How much area does a bag of mulch cover?
A 2 cu ft bag covers about 8 sq ft at 3 inches deep, 12 sq ft at 2 inches, or 24 sq ft at 1 inch.
Is bulk mulch cheaper than bags?
Usually, once you need more than 2–3 cubic yards. Bulk is sold by the yard, but delivery fees can make small orders more expensive than bags.
How often should I replace mulch?
Organic mulch breaks down over time. Most beds need a 1-inch top-up each year and a fuller refresh every 2–3 years.