Mulch is sold in two very different ways — small bags at a big markup per cubic yard, or bulk delivery that’s cheaper but requires you to know exactly how much to order. Our mulch calculator converts your garden bed’s area and desired depth into both cubic yards (for bulk orders) and bag count (for a quick hardware-store run).
The math
Cubic feet = area (sq ft) × (depth in inches ÷ 12)
Cubic yards = cubic feet ÷ 27
Bags needed = ceiling(cubic feet ÷ bag size)Example
A 200 sq ft bed, 3 inches deep, standard 2-cubic-foot bags:
- Cubic feet: 200 × (3/12) = 50 cu ft
- Cubic yards: 50 ÷ 27 = 1.85 cu yd
- Bags: ceil(50 ÷ 2) = 25 bags
Choosing a depth
Most landscaping guidance recommends 2-3 inches for established beds — enough to suppress weeds and retain soil moisture without smothering plant roots. Piling mulch 4+ inches deep (sometimes called “volcano mulching” when done around tree trunks) can trap excess moisture against stems and promote rot or fungal growth — more isn’t better past a certain point.
Bags vs bulk
For small beds (under roughly 3 cubic yards), bagged mulch is usually the more convenient option despite a higher per-cubic-yard cost. For larger areas, ordering bulk mulch by the cubic yard from a landscaping supplier is significantly cheaper — this calculator shows both units side by side so you can compare and decide which purchasing route makes sense for your project size.