Topsoil math is the same volume formula as mulch or gravel: area times depth, divided by 324 to get cubic yards. The decisions that matter are quality (what's actually in the soil), depth (different for raised beds vs lawn fill vs topdressing), and bulk vs bagged. Here's the practical version with what to check at the supply yard before they load the truck.

The volume formula

All soil and aggregate sold by the yard uses this:

cubic yards = area_ft² × depth_in ÷ 324

Example: a raised bed 8 ft × 4 ft, filled to 6 in. (8 × 4 × 6) ÷ 324 = 192 ÷ 324 = 0.59 yd³. Round up to a yard for delivery (most yards have a 1-yard minimum) or buy 22 bags of 40 lb topsoil at a home center (~0.75 ft³ per bag).

The topsoil calculator runs this and tells you when bulk delivery beats bags on cost.

Depth by use case

  • Raised vegetable bed: 8-12 in deep — vegetables need root depth, especially carrots, parsnips, and tomatoes
  • Raised flower bed: 6-8 in is plenty for annuals and most perennials
  • New lawn over graded subsoil: 4-6 in of topsoil before seed or sod
  • Lawn fill (low spots, settling repairs): 2-4 in, then re-seed
  • Topdressing existing lawn: 0.25-0.5 in per pass — improves soil over time without smothering grass
  • Berms and grade changes: Whatever the design needs, but stop above the trunk flare on existing trees (suffocates roots)

For raised beds specifically, the cheapest fill strategy is the “hügelkultur” layered approach: branches and logs at the bottom (free, decomposes over years), compost in the middle, premium topsoil only at the top 6-8 in where the roots actually grow. Cuts topsoil order in half.

What “topsoil” actually means at the yard

Topsoil isn't a regulated term. What you get varies wildly:

  • Screened topsoil: Run through a 1/2-inch screen to remove rocks, roots, debris. Most common bulk product. $25-40/yd³ delivered.
  • Pulverized topsoil: Screened plus mechanically ground for fine texture. $35-50/yd³. Better for seeding lawns.
  • Topsoil blend: Topsoil mixed with compost (30-50% organic). $45-70/yd³. Premium for raised beds.
  • Garden soil / planting mix: Heavily amended with compost, peat, sometimes fertilizer. $60-100/yd³. Best for vegetables.
  • Fill dirt: Subsoil or excavation spoil. NOT topsoil — no organic matter, won't grow grass. Cheapest at $15-25/yd³ but only useful for raising grade or filling holes.

Ask before ordering: “Is this screened topsoil or fill?” A surprising amount of “topsoil” sold cheap is actually fill dirt with a different label. Eyeball the pile — good topsoil is dark brown to black, crumbly, and smells slightly earthy. Fill is gray or yellow-tan and packs hard.

Bulk vs bagged — the breakeven

The math heavily favors bulk past about 1 cubic yard:

  • Bagged 40 lb (0.75 ft³ each): $5-8 per bag at home centers. 1 yd³ = 36 bags = $180-290 plus 36 trips lifting bags.
  • Bulk delivered: $25-50 per yd³ delivered. Same 1 yd³ = $25-50, dumped wherever you can have a 5-yard pile.

Bagged makes sense under 1 yd³ (about 36 bags) — when you can't justify a delivery fee, when the project is in a tight space without dump access, or when matching a premium amended mix the bulk yard doesn't carry. Past 1 yd³, bulk wins by 4-6×.

What pros do differently

Order 10-15% extra. Soil compacts during delivery and again as you spread it. A yard ordered loose becomes 0.85-0.9 yd³ once installed and watered. Round up.

Stage the dump on a tarp. Topsoil dumped on grass kills the lawn under it within a day. Tarp the dump zone, pile the dirt on the tarp, drag the tarp away when finished. Saves resodding the dump area afterward.

Time delivery to a dry day. Wet topsoil weighs 30% more, compacts harder, and is impossible to spread evenly. Same yard of soil is half the work to install dry.

Quick FAQ

How much does a yard of topsoil weigh? About 1,800-2,400 lb depending on moisture and organic content. A pickup bed legally hauls about half a yard.

How much topsoil for a 200 ft² raised bed at 10 in? (200 × 10) ÷ 324 = 6.2 yd³. Order 7 yd³ to allow for compaction.

Is bagged topsoil sterilized?Some brands are heat-treated; most aren't. For seed-starting mixes, look for products labeled sterile. For raised beds and lawns, regular topsoil with weed-seed potential is fine — you'll be weeding anyway.

Mulch on top of the soil? Run the mulch calculator for the same project — mulch goes on at 2-3 in over fresh topsoil to reduce weeds and water loss.