Soil Calculator – Raised Garden Bed Dirt Calculator

How the Soil Calculator Works

Pick a shape (rectangle, circle, or custom area), enter dimensions and fill depth, the number of beds, and an optional compaction allowance. The calculator converts everything to feet, computes area and volume for a single bed, multiplies by the number of beds, adds your extra %, and returns totals in cubic feet, cubic yards (÷27), and bags (1.5, 2, 3 cu ft plus your custom size).

Worked Example: 4×8 Raised Bed, 12″ Deep

Area = 4×8 = 32 ft². Volume = 32 × (12 ÷ 12) = 32 cu ft = 1.185 cu yd. With 10% extra: 35.2 cu ft (1.30 cu yd). That’s 18 bags (2 cu ft) or 12 bags (3 cu ft). With the default 40/40/20 mix: Topsoil 14.1 cu ft, Compost 14.1 cu ft, Aeration 7.0 cu ft.

FAQs – Raised Garden Bed Soil & Dirt Calculator

How much dirt for a raised bed?

Multiply bed area (length×width for rectangles; 0.785×diameter² for circles) by depth (inches ÷ 12) to get cubic feet. Add 5–15% for settling.

How many bags of soil are in a cubic yard?

1 cubic yard = 27 cu ft → 18 bags (1.5 cu ft), 14 bags (2 cu ft), or 9 bags (3 cu ft).

What soil mix should I use for raised beds?

A popular starting point is 40% topsoil, 40% compost, 20% aeration (perlite, pumice, rice hulls). Adjust to your plants and drainage.

How do I calculate soil for multiple beds?

Enter one bed’s dimensions and set Number of Beds. The calculator multiplies and shows both total and per-bed volumes.

Garden bed square foot method?

Use square footage (ft²) and depth. Example: 100 ft² × (10″ ÷ 12) = 83.3 cu ft ≈ 3.1 cu yd ≈ 42 bags (2 cu ft).

Can I use metric?

Yes—choose meters/centimeters. Results still show cu ft and cu yd, plus liters for convenience (1 cu ft ≈ 28.316 L).

Notes

• Dimensions assume internal bed size (usable soil space).
• Compaction and moisture change volume—round up if unsure.
• For mixes bought per component, use the breakdown to buy materials separately.