Garden Bed Volume Calculator

Raised beds and planter boxes need a known volume of soil mix before you order compost, topsoil, or bagged potting blend. Volume equals length × width × depth — the same geometry as mulch, but planting beds are usually deeper to give roots room. US mode accepts feet for length and width with depth in inches; metric uses meters and centimeters.

Most vegetables need 8–12 inches (20–30 cm) of quality mix at minimum. Root crops like carrots and potatoes often want 12–18 inches. Herbs and shallow greens can succeed in 6-inch troughs. Match depth to the deepest-rooted crop you plan to grow in that bed, not to the shallowest neighbor.

Soil settles after the first few waterings — buy 5–10% extra for topping off. A blend of topsoil, compost, and aeration (perlite, vermiculite, or coco coir) drains better than straight garden dirt scraped from the yard. Many gardeners use roughly one-third compost by volume for new beds.

Bulk soil is sold by the cubic yard or cubic meter; bagged mixes list cubic feet or liters on the label. Compare unit prices after converting to the same volume unit. Delivery trucks need gate clearance and a firm path — measure access before ordering a full yard dump.

Tiered or stepped beds require calculating each rectangle separately and adding volumes. L-shaped beds split into two rectangles the same way. Internal framing boards reduce usable volume slightly; this calculator assumes the interior planting dimensions you enter.

Container mixes differ from in-ground soil — potting soil is lighter and more expensive per volume. Do not fill a large raised bed entirely with peat-heavy bagged mix unless budget allows; many growers cap expensive blend in the top 6 inches and use lower-cost fill below. Hardware cloth under the bed deters burrowing pests without changing volume math.

Double-check interior dimensions if your kit lists nominal board sizes — a "4×8" store label may measure slightly smaller inside the lumber. Measuring with a tape after assembly beats trusting marketing labels when ordering soil by the cubic yard.

Worked example with default inputs: an 8 ft × 4 ft bed at 12 inches deep holds 32 cubic feet of mix, about 1.19 cubic yards, or roughly 906 liters. That is enough for a standard 4×8 raised kit filled to one foot. Order a tenth yard extra if you expect settling after rain, and keep a wheelbarrow path clear for delivery dumps.