Raised Bed Soil Calculator

How to calculate raised bed soil

1. Measure inside the bed — from the inside face of board to inside face; never the outside.
2. Set the fill depth — the actual soil depth you want (common presets: 4, 6, 8, 12 in), not necessarily the board height.
3. Count the beds — identical beds can be multiplied per section with the beds input.
4. Add soil mix optionally — enter topsoil/compost/amendment percents that total 100 for a per-component order list.
5. Price it — bag price or bulk per yard; the comparison shows both once entered.

The formulas

Volume per bed (cu ft)  = interior length x width x fill depth   (all in feet)
  circular beds         = 3.1416 x (interior diameter/2)^2 x fill depth
Total volume            = per-bed volume x number of beds
Volume (cu yd)          = Total / 27
Bags                    = round-up(Adjusted cu ft / bag size)

A note on simplified geometry: this assumes a simple prism of soil whose top face is level — irregular beds (terraces, mounds, beds with built-in bases or partial fill) don't fit the model, so measure conservatively and confirm with your supplier. See the calculation methodology.

Worked example

One 4 × 8 ft bed (interior), boards 12 in tall, filled to the top: 4 × 8 × 1 = 32 cu ft ≈ 1.19 cu yd. Three identical beds at 10 in of fill would instead be 3 × (4 × 8 × 10/12) = 80 cu ft ≈ 2.96 cu yd — roughly 40 two-cubic-foot bags, or a bulk delivery at ~3 yards.

Measuring tips

• For round planters, measure the inside diameter at the widest point.
• Beds with a divider: treat each half as its own section.
• Existing soil in the bottom counts toward depth — set fill depth to what you're actually adding.

Common soil ordering mistakes

• Using the exterior 4×8 size printed on a kit box, then wondering why 2.5 yards wouldn't fit — interior inches matter.
• Ordering by fill depth to the brim when the bed will settle an inch or two on first watering.
• Buying a "cubic yard" of bagged soil — bags are sold in cubic feet, and 27 of them sit on a pallet.
• Mixing ratios by weight vs by volume; our mix breakdown stays in volume to match how bags and yards are sold.

Frequently asked questions