Raised Bed Soil Calculator

The raised bed soil calculator estimates how much soil, compost, and amendments to buy for one raised garden bed or a whole garden of mixed-size beds. Bed dimensions and a soil mix recipe convert into total volume in cubic feet and cubic yards, approximate weight, bag counts, and material cost. Supported shapes are rectangular, circular, and L-shaped beds, in either imperial or metric units.

• Imperial units use feet, inches, and pounds; metric units use meters, centimeters, and kilograms.
• Rectangular beds use length and width; circular beds use a single diameter value entered in the width field; L-shaped beds apply a 75 percent area factor to the bounding rectangle.
• Width and length accept decimals (3.5), fractions (7/2), and mixed numbers (3 1/2).
• Most vegetables need 6 to 12 inches (15 to 30 cm) of soil depth.
• A quantity multiplies a bed's own volume in the total, for several identical beds of the same size.
• Beds of different dimensions or shapes can be added as separate rows; volumes from every bed sum into the total.
• A 60/40 topsoil-to-compost mix suits most vegetables, Mel's Mix suits square foot gardening, and a custom recipe sets its own percentages.
• Results include total volume, weight, bag counts, estimated cost, and a soil mix breakdown.
• Settings can adjust the cost per cubic foot for each material, the assumed soil weight, or reveal the step-by-step formula display.

Per-bed volume formulas: Rectangular = Length x Width x Height, Circular = pi x (Diameter / 2) squared x Height, L-Shaped = 0.75 x Length x Width x Height. Each volume is multiplied by Quantity and then summed across all beds. Weight defaults to 40 lbs per cubic foot, and cubic yards equal cubic feet divided by 27.

A standard 4 by 8 foot bed filled to a 12-inch (1 foot) depth has a volume of 4 x 8 x 1 = 32 cubic feet, equal to 32 / 27 = 1.19 cubic yards, and an estimated weight of 32 x 40 = 1,280 pounds at the default 40 pounds per cubic foot.

Accurate soil estimates, made before purchasing materials, keep a raised bed project from over-buying or running short. Rectangular, circular, and L-shaped beds combine into one estimate regardless of how a garden mixes shapes.

• Backyard Gardening: how many bags of soil a standard 4 x 8 foot raised bed needs, compared against bulk delivery cost.
• Mixed-Size Gardens: two 4 x 8 rectangular beds (quantity 2), a 6-foot diameter round herb bed, and an L-shaped corner bed combine into one total; the cubic-yard figure is the bulk order.
• Square Foot Gardening: Mel's Mix (1/3 compost, 1/3 peat moss, 1/3 vermiculite) gives exact quantities for each component, with cost settings comparing prices across suppliers.
• Community Gardens: a row for every plot size, each with its own quantity, lets the cumulative cost split fairly across members using the breakdown.
• Landscaping Projects: the circular bed shape suits round planters or tree rings, alongside rectangular rows for adjacent borders; metric units suit projects using metric lumber and soil measurements.
• Budget Planning: cost per cubic foot in Settings matches local pricing, and different soil mix recipes compare on total cost before a purchase.
• Season Preparation: how much additional compost to add each spring follows from settling: soil settles 10 to 15 percent in the first season, so beds need an annual top-off compost layer.
• Hugelkultur Beds: beds deeper than 12 inches need soil volume estimated only for the top 12 inches; the bottom fills with logs, sticks, or leaves to reduce cost and improve drainage.
• Education: volume calculations teach through real garden dimensions, with the step-by-step formula display showing the math behind each bed and the running total.