Mulch Calculator
Figure out how many cubic yards or bags of mulch you need for any garden bed — by length, width, and depth.
What is Mulch Calculator?
The mulch calculator turns a garden-bed measurement into a purchase list — cubic yards for bulk delivery (the cheaper option for 2+ yards), or retail bags if the job is small.
Apply mulch 2–4 inches deep: shallower dries out too fast, deeper can smother plant roots.
Formula
Area = length × width (square feet)
Cubic feet = area × (depth in inches / 12)
Cubic yards = cubic feet / 27
Standard U.S. retail mulch bags are 2 cubic feet. One cubic yard covers:
- 162 sq ft at 2" deep
- 108 sq ft at 3" deep
- 81 sq ft at 4" deep
Worked example
A 20 × 4 ft foundation bed at 3 inches deep:
- Area = 80 sq ft
- Cubic feet = 80 × 0.25 = 20 cu ft
- Cubic yards = 20 ÷ 27 ≈ 0.74 cu yd
- Retail bags (2 cu ft each) = 10 bags
Bulk delivery typically has a 1-yard minimum and works out to about half the per-yard cost of bagged mulch.
How to use this calculator
- Measure each garden bed's length and width in feet. For irregular shapes, split into rectangles and add.
- Decide on depth: 2" for annuals, 3" for shrubs and established beds, 4" for weed suppression.
- If ordering bulk, round up to the nearest quarter yard. If buying bags, the calculator already rounds up.
Frequently asked questions
How much does a cubic yard of mulch weigh?
Hardwood: ~800–1,000 lb per cu yd. Softwood (pine bark, cedar): ~500–800 lb. Rubber: ~1,500 lb. Most half-ton pickup beds can haul 1 cu yd of hardwood safely; a full-size pickup handles 2 yards.
Bulk or bagged — which is cheaper?
Bulk mulch typically costs $25–$40 per cubic yard delivered. Bagged mulch at big-box stores runs $3–$5 per 2-cu-ft bag = $40–$67 per equivalent cubic yard. Bulk wins for anything over 1 yard.
When should I replace mulch?
Natural wood mulch breaks down over 1–2 years. Add 1 inch annually to maintain depth. Fully refresh every 2–3 years, removing old matted layers first so water can penetrate.
Is dyed mulch safe?
Most commercial dyed mulches use iron oxide (for red) or carbon black (for dark) — both are non-toxic. Avoid products made from CCA-treated demolition wood, which is labeled "avoid for gardens" for good reason.