Mulch Calculator
Calculate cubic yards of mulch for any garden bed from area dimensions and desired depth.
Supports 2, 3, and 4-inch coverage with bag count estimates.
Mulch quantity calculation determines how many cubic yards or bags of mulch you need to cover a garden bed to a specified depth. Proper mulch depth is critical — too shallow fails to suppress weeds and retain moisture; too deep can suffocate plant roots and harbor pests.
Core formula: Volume (cubic feet) = Area (sq ft) × Depth (ft) Volume (cubic yards) = Volume (cubic feet) ÷ 27 Bags needed = Volume (cubic feet) ÷ Bag Size (cubic feet)
Note: Depth must be in feet (divide inches by 12 before calculating).
What each variable means:
- Area — the square footage of the garden bed to be mulched. For irregular shapes, break into rectangles and sum, or use length × width for a conservative estimate.
- Depth — desired mulch layer thickness. The recommended depth depends on mulch type and purpose.
- Cubic yards — the standard unit for bulk mulch delivered by truck. 1 cubic yard = 27 cubic feet.
- Bag size — bagged mulch is sold in 2 cubic foot bags (most common) or 3 cubic foot bags at home improvement stores.
Recommended mulch depths by purpose:
| Purpose | Recommended Depth |
|---|---|
| Weed suppression | 3–4 inches |
| Moisture retention | 2–3 inches |
| Tree/shrub rings | 3–4 inches (keep away from trunk) |
| Vegetable garden paths | 4–6 inches |
| Playground safety surfacing | 9–12 inches |
Mulch types and coverage:
- Shredded hardwood bark — most common, lasts 2–3 years, good weed suppression
- Pine bark nuggets — decorative, slower to decompose, poor weed suppression
- Cedar mulch — natural pest deterrent, lasts 3–5 years
- Rubber mulch — extremely long-lasting (10+ years), used for playgrounds
- Straw — lightweight, best for vegetable gardens, breaks down quickly
Worked example: Garden bed: 15 ft × 20 ft = 300 sq ft. Desired depth: 3 inches = 0.25 ft.
Volume = 300 × 0.25 = 75 cubic feet Cubic yards = 75 ÷ 27 = 2.78 cubic yards (order 3 yards) Bagged (2 cu ft bags) = 75 ÷ 2 = 37.5 bags (buy 38 bags)
Bulk delivery is almost always cheaper for areas over 250 sq ft. At $40–$60/cubic yard delivered vs. $6–$8 per 2 cu ft bag ($3–$4/cu ft), bulk saves 25–50%.