Garden Soil Calculator
How Much Soil Does a New Bed Actually Need?
A garden bed's soil volume scales with three dimensions at once, so doubling the depth or the width has a much bigger effect on the total than most people expect. Underestimate it and a delivery truck comes back for a second load; overestimate and topsoil sits in a pile losing structure in the rain. This calculator works the length, width, and depth into an exact cubic-foot and cubic-yard figure, plus a bag count if you're buying bagged soil instead of bulk.
The Formula
Volume (cu yd) = Volume (cu ft) ÷ 27
Bags Needed = ceil(Volume (cu ft) ÷ Bag Size)
Length and width are in feet; dividing depth by 12 converts inches into feet so all three dimensions share the same unit before multiplying. Bag count rounds up, since a partial bag still has to be purchased whole.
Worked Example
A 10 ft × 5 ft bed filled to 6 inches deep:
| Quantity | Value |
|---|---|
| Cubic feet | 25.0 cu ft |
| Cubic yards | 0.926 cu yd |
| 1.5 cu ft bags needed | 17 bags |
Where This Calculation Matters
- New in-ground beds — amending native soil with a set depth of topsoil or garden blend before the first season.
- Bulk vs. bagged decisions — most bulk suppliers have a minimum order (often 1 cu yd); this calculator shows whether a project clears that threshold or is cheaper bought in bags.
- Budgeting soil delivery — bulk soil and compost are typically priced per cubic yard, so an accurate yardage figure avoids over- or under-ordering a delivery.
How to Use This Calculator
- Enter the bed length in feet.
- Enter the bed width in feet.
- Enter the desired soil depth in inches.
- Optionally enter your bag size in cubic feet to get a bag count alongside the bulk volume.
- Select Calculate to get the total volume needed.
Related Calculations
Filling several identical beds at once? The Raised Bed Soil Calculator multiplies this same formula across multiple beds. For topdressing rather than a full fill, see the Compost Calculator.