Topsoil is sold by the cubic yard, the ton or the bag, and the ground is measured in square feet. The volume is the same arithmetic as mulch — one cubic yard covers 324 square feet an inch deep — and the weight is the part to be careful with.
This page weighs soil at 1.33 grams a cubic centimetre, the bulk density Penn State uses “because this approximates the bulk density of a silt loam soil”: 83 pounds a cubic foot, or about 1.12 tons a cubic yard. That is dry soil, in place. Sandy soil is heavier and soil rich in organic matter lighter, Penn State says, and what a truck delivers holds water — so when a supplier quotes tons a yard, use their figure.
The depths are the sources’ own:
- 4 to 6 inches of good topsoil, “firmed or settled depth”, to establish a lawn — Penn State’s lawn guide. It has 2 inches of it worked into the top 2 to 3 inches of the subsoil, so the two do not sit as separate layers. Settled means what it says: loose soil sinks, and the extra field is for that.
- 8 inches for a raised bed of leafy greens, beans and cucumbers, and 12 to 24 inches for peppers, tomatoes and squash — the University of Maryland’s raised-bed guide. It fills a bed on soil with compost and topsoil “in a 1:2 or 1:1 ratio”, and the mix field shares the volume out that way.
Measured an odd-shaped bed on the calculator? Follow its link here and the area comes with it.