Topsoil Calculator

Penn State Extension and New Mexico State University both put it at 4 to 6 inches of good topsoil, and both mean the depth after the soil has firmed and settled. NMSU calls 4 inches the absolute minimum and recommends 6 or more for deeper roots. The same depth applies whether you seed or lay sod, since NMSU says the soil preparation is the same for both.

UC Master Gardeners give 6 to 12 inches as the standard raised bed depth, with the deeper end for root crops like carrots and potatoes. For the volume, multiply length × width × depth in feet. An 8 × 4 ft bed filled 12 inches deep holds 32 cubic feet, which is 1.19 cubic yards. With a 10% settling allowance that's 24 bags of 1.5 cu ft.

A cubic yard is 27 cubic feet. That comes to 36 bags of 0.75 cu ft, 27 bags of 1 cu ft, or 18 bags of 1.5 cu ft. Topsoil sold as a 40 lb bag usually holds about 0.75 cu ft, so count it like the smallest size. Check the cubic feet printed on the bag, because that is what fills the space, not the weight.

Select Sand & Gravel, a soil supplier, puts a cubic yard of topsoil at 2,100 to 2,600 lb, uses 2,300 lb (about 1.15 US tons) for planning, and says wet topsoil can reach 3,000 lb or more. That lines up with USDA NRCS, which gives about 1.33 g/cm³ for a medium-textured soil, roughly 2,240 lb per cubic yard. The calculator starts at 2,300 lb, and you can type your supplier's figure over it.

Freshly spread topsoil is loose and sinks after the first few rains or waterings. Select Sand & Gravel suggests ordering about 10% more than the measured volume. On deep fills, plan for more: Purdue turf specialists note that each foot of soil moved can settle up to 2 inches, which is about 17%.

It depends on your local prices and the delivery fee, so the calculator lets you enter both and shows the totals side by side. Bags make sense for patching a few bare spots or topping up a bed, where the delivery charge on a bulk load would cost more than the soil. A new lawn or several raised beds needs dozens or hundreds of bags, and at that point bulk usually wins once you add the delivery fee to the bulk total.

A ¼ inch layer over 1,000 sq ft takes 0.77 cubic yards, which matches the table in the Guelph Turfgrass Institute's sports turf newsletter. That newsletter describes ¼ inch twice a season for sports fields and 1/8 inch for leveling. Penn State notes that only about ¼ to ½ inch of material can be worked in with a core aerator during renovation, so keep the layer thin enough that the grass shows through.