What this calculator does and when to use it
This calculator converts the dimensions of up to four different project areas — raised beds, in-ground garden beds, lawns needing a topsoil layer, and general fill areas — into the volume of soil you need to buy, in cubic yards (the unit most soil, mulch, and compost is sold by at garden centers and bulk suppliers). Filling any project's fields adds that project's volume to a running total, so you can price out a whole yard's worth of projects in one calculation rather than doing separate math for each bed.
Use it before ordering bagged or bulk soil for a new raised bed, before tilling in fresh topsoil or compost across an existing garden plot, before top-dressing or releveling a lawn, or before filling a low spot, trench, or planter with fill dirt. Getting the volume right up front avoids the common problem of running out mid-project or over-ordering and paying for soil you don't need.
The formula
Each project type uses the same core volume formula, with a different assumed depth where the form doesn't ask for one:
- Volume (cubic feet) = Length (ft) × Width (ft) × Depth (ft), where Depth (ft) = Depth (inches) ÷ 12.
- Raised beds use your entered depth and can multiply by a bed count for multiple identical beds.
- Garden beds assume a standard 6-inch tilling/amendment depth; you only enter length and width.
- Lawns assume a standard 2-inch topsoil layer for leveling or overseeding prep; you enter total square footage directly.
- Fill areas let you specify any custom depth for general-purpose filling.
The calculator sums cubic feet across every project you filled in, converts to cubic yards (1 cu yd = 27 cu ft), and adds a 10% buffer to the recommended purchase amount to account for settling and minor measurement error — a common rule of thumb among landscapers.
Worked example
For a single raised bed measuring 4 feet by 8 feet, filled to a 12-inch depth: Volume = 4 × 8 × (12 ÷ 12) = 32 cubic feet. Converting to cubic yards: 32 ÷ 27 = 1.19 cu yd. Adding the 10% buffer: 1.19 × 1.10 = 1.30 cu yd recommended purchase — matching exactly what the calculator returns when you enter length 4, width 8, and depth 12 for a single raised bed.
Common mistakes and how to interpret the result
- Entering depth in feet instead of inches. The depth fields expect inches (a typical raised bed is 8-12 inches deep) — entering "12" meaning 12 feet would produce a wildly inflated volume.
- Forgetting the bed count for multiple identical raised beds. If you're building several beds of the same size, enter the count in "Number of Beds" rather than calculating one bed and manually multiplying — the field is there to do that for you.
- Skipping the 10% buffer when ordering. Settling, compaction, and minor measurement error mean the exact calculated volume often falls slightly short — the "recommended purchase" figure already accounts for this and is the number to bring to the store.
- Mixing bagged and bulk soil units. Bagged soil is typically sold in cubic feet (a common bag is 1.5 or 2 cubic feet), while bulk soil is sold by the cubic yard — convert cubic yards to cubic feet (× 27) if you're buying bags instead of bulk delivery.