Garden Berm Calculator

A garden berm is a raised mound of soil. People build them to divert drainage, screen a view, knock down road noise, break up a flat yard, or simply to get a planting bed up out of heavy ground. Working out the soil means treating the mound as a geometric shape, and the one that fits a natural berm best is half an ellipsoid.

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

That is half an ellipsoid, and it tracks a real soil mound closely.

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

This assumes a triangular cross-section, so it comes out a little under 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 the ellipsoid formula)

Enter the height you want to end up with

Not the height you intend to pile it to. The calculator adds the settling allowance itself, so if you type 3 feet it works out the soil for a berm that is 3 feet tall after a year. Typing 3.5 because you have already allowed for settling counts it twice and lands you with a truckload you did not need.

Topsoil weight and delivery: One cubic yard of topsoil weighs about 1.1 tons (2,200 lbs), the same figure the Topsoil Calculator uses. In metric that is 1.3 tonnes per cubic metre. A standard tandem dump truck load is 10 to 15 cubic yards. As a rough US guide in 2025, bulk topsoil runs $15 to $50 a cubic yard delivered, varying enormously by region and by how well it is screened.

Berm design guidelines:

• Slope ratio: the flattest side should be no steeper than 3:1, three feet horizontal for every foot of vertical, in ordinary soil. Steeper than that and you need a retaining structure or rock facing, or you will be raking the bottom of it back up the slope after every storm.
• Height for privacy: a 6-foot berm screens a standing view, 4 feet screens seated views, and 8 feet or more starts to do something measurable about noise.
• Width-to-height ratio: figure 4 to 6 feet of base width for every foot of height. A 3-foot berm wants to be 12 to 18 feet across the bottom, which is far wider than most people picture.
• Settling: new soil berms lose 10 to 20% of their height in the first year. This calculator adds 15%, the middle of that range. Sandy fill settles less. Anything with a lot of organic matter in it settles more, and keeps going for a second season.

Soil amendment needs: Pure fill dirt is too dense to plant into. The usual approach is a cheap fill core with a good growing layer over the top: 70% fill dirt to 30% compost by volume through the upper 12 inches is the standard plantable mix, and that is the ratio this page uses throughout.

Worked example: A berm 20 feet long, 8 feet wide at the base, 3 feet tall when it has finished settling.

• Volume: (π × 20 × 8 × 3) ÷ 6 = 1,507.96 ÷ 6 = 251.3 cubic feet
• Cubic yards: 251.3 ÷ 27 = 9.3 cubic yards
• With the 15% settling allowance: 10.7 cubic yards, so order 11
• Weight: about 11.8 tons, which is one dump truck load. Bagged, it would be 386 of the small 0.75 cu ft bags.
• At $30 a yard delivered: 11 × $30 = $330

That last line is why berms get built out of whatever fill the neighbour is digging out for a pool. Bulk fill dirt runs a fraction of screened topsoil, and only the top foot has to be any good.