Calculate Soil or Mulch Volume
Works for raised beds, flower beds, lawn topdressing, and any other rectangular area. Enter your measurements and select your bag size.
- Vegetable raised bed: 12 inches (30 cm) of soil
- Flower bed: 6–8 inches of soil
- Mulch layer: 2–3 inches (replenish yearly)
- Lawn topdressing: ¼–½ inch of compost
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How Much Soil Do I Need for a Raised Bed?
The volume formula is simple: length × width × depth. The tricky part is converting between units. A standard 4×8 foot raised bed filled 12 inches deep needs 32 cubic feet of soil — that's about 16 two-cubic-foot bags or 1.2 cubic yards from a bulk supplier.
Buying in bulk (by the cubic yard) is almost always cheaper than bagged soil once you need more than about 2–3 cubic yards. A cubic yard is 27 cubic feet, which equals about 13–14 standard 2-cu-ft bags.
Soil vs. Mulch: What's the Difference?
Soil fills and feeds your bed — it's the growing medium where roots live. Mulch sits on top to retain moisture, suppress weeds, and regulate soil temperature. You need both in most garden setups, just in very different depths.
For soil, use a quality raised bed mix (not pure topsoil, which compacts). For mulch, wood chips, straw, and shredded leaves all work well. Avoid dyed mulches near edible plants.
Bulk vs. Bagged: Which Is Better?
For small projects (under 1 cubic yard), bagged soil is more convenient. For anything larger — like filling multiple raised beds — bulk delivery from a landscape supply yard is significantly cheaper. Most suppliers have a 1-cubic-yard minimum delivery.