How much soil do I need to fill two 8 × 4 ft raised beds, 12 inches deep?
For the worked example (2 beds, each 8 × 4 ft, filled 12 in deep) the material list is Raised-bed soil: 2.37 yd³ (calculated 2.37 yd³, based on 2 beds, 12 in fill depth, no allowance). Quantities to buy are whole units rounded up from the calculated amounts. Enter your own measurements in the calculator above for your exact list.
How to use this calculator
- Enter how many beds you have and their length and width.
- Enter the depth of soil each bed takes.
- Pick a bag size if you are buying bagged soil.
- Optionally split the total into a mix by entering your own percentages.
- Copy, print or share the material list.
How this is calculated
- Per bed (cu ft) = length × width × fill depth (ft), with depth in inches ÷ 12
- Total = per bed × number of beds
- Cubic yards = cubic feet ÷ 27
- Bags = round up (cubic feet ÷ cubic feet per bag)
- Mix component = total × its percentage (percentages must total 100%)
Geometry is deterministic. Material coverage, density, installation waste and product yield can vary. We expose those assumptions so you can replace them with the values printed on the products you are actually buying. Treat every result as an estimate. Items on your list are labelled Calculated (straight from your measurements) or Estimated (depends on an assumption), and “Buy” quantities are whole units rounded up.
Sources
- University of Minnesota Extension – Raised bed gardens. Context only: raised-bed mixes of roughly one-half to two-thirds topsoil with the remainder largely plant-based compost. Used only as background text beside the optional mix. It never sets your percentages.
Last reviewed: . See the methodology.
Assumptions
These starting values are used until you change them. They are typical, not universal. Check the label on the product you are buying.
| Assumption | Starting value | Where it comes from |
|---|---|---|
| Cubic feet in a cubic yard | 27 | Mathematical – 3 ft × 3 ft × 3 ft |
| Inches in a foot | 12 | Mathematical – Depth in inches ÷ 12 gives feet |
| Custom bag size | You enter it | You enter it (product / supplier) |
| Topsoil (optional) | You enter it | Common planning default |
| Compost (optional) | You enter it | Common planning default |
| Other (optional) | You enter it | Common planning default |
Worked example
Two beds, each 8 × 4 ft, filled 12 in deep, with 1.5 cu ft bags:
- Raised-bed soil: 2.37 yd³ (or 43 × 1.5 cu ft bags) · 2 beds, 12 in fill depth, no allowance
Common questions
What soil mix should I use?
That depends on your plants and local conditions, so we do not fill one in. University of Minnesota Extension describes roughly one-half to two-thirds topsoil with the rest largely plant-based compost as a starting context. Your own plan or your supplier’s advice should decide your percentages.
Do I need to fill beds to the top?
Beds settle, and people fill to different heights. Enter the depth you intend to fill, and add soil later if it settles.
Is bulk cheaper than bags?
Often for larger volumes, but prices vary. Enter your own bulk and bag prices under “Estimate cost (optional)” to compare.