Garden Berm Calculator

Garden berm is a raised mound of soil — used for drainage diversion, privacy screening, noise buffering, landscape aesthetics, or creating elevated planting beds. Calculating soil volume requires treating the berm as a geometric shape (typically a flattened cone or half-ellipsoid).

Berm volume — elliptical mound approximation: For a berm with an elliptical footprint and smooth dome profile: Volume = (π × Length × Width × Height) ÷ 6

This is equivalent to half of an ellipsoid, which closely approximates a natural soil mound.

Simpler trapezoidal cross-section model: Volume = (1/2) × Base Width × Height × Length

This assumes a triangular cross-section — slightly underestimates a rounded berm.

Converting volume to cubic yards (US standard): Cubic Yards = Cubic Feet ÷ 27 Cubic Yards = (Length ft × Width ft × Height ft × π) ÷ 162 (using ellipsoid formula)

Topsoil coverage: One cubic yard of topsoil weighs approximately 1 ton (2,000 lbs) when moist. A standard dump truck load: 10–15 cubic yards. Bulk topsoil price: $15–$50 per cubic yard delivered (varies by location and quality).

Berm design guidelines:

• Slope ratio: Maximum recommended slope for stability = 3:1 (3 feet horizontal per 1 foot vertical) for stable soil. Steeper slopes require retaining structures or rock facing.
• Height for privacy: A 6-foot berm provides visual screening; 4 feet screens seated views; 8+ feet provides noise buffering
• Width-to-height ratio: Typical berm is 4–6 feet wide for every 1 foot of height, a 3-foot tall berm should be 12–18 feet wide at the base
• Settling: New soil berms settle 10–20% over the first year, build higher than target

Soil amendment needs: Pure fill dirt is too dense — add compost or topsoil to the upper 12 inches for planting. Mix: 70% fill dirt + 30% compost by volume for a plantable berm.

Worked example: Berm dimensions: 20 feet long, 8 feet wide (base), 3 feet tall. Target height after 15% settling: build to 3.5 feet.

• Volume: (π × 20 × 8 × 3.5) ÷ 6 = (3.1416 × 560) ÷ 6 = 1,759.3 ÷ 6 = 293.2 cubic feet
• Cubic yards: 293.2 ÷ 27 = 10.86 cubic yards → order 11 yards
• Weight: 11 × 1 ton = ~11 tons of soil (requires dump truck delivery, not bagged)
• Cost: 11 × $30 = $330 in bulk topsoil