How much topsoil to level a lawn?

How the number is worked out

Volume is area × depth with the depth converted from inches to feet. A 4 ft × 8 ft raised bed filled 12 in deep is 32 × 1 = 32 cubic feet, or 1.19 cubic yards, before any settling allowance.

Bagged topsoil is not the same stuff as bulk topsoil

This is the thing almost nobody says out loud. Take the most widely stocked bagged product, Scotts Premium Topsoil: 0.75 cubic feet, 14 pounds. That works out to roughly 500 lb per cubic yard. Bulk screened topsoil from a landscape yard is 2,000–2,700 lb per cubic yard.

The bagged product is about a quarter of the density, because it is largely sphagnum peat moss and organic matter — the label calls it a soil conditioner. It is a fine amendment and a fine top-up for a lawn patch. It is not mineral soil, and a bed filled entirely with it will hold water like a sponge and collapse as the peat breaks down.

If you need actual soil in volume, buy bulk and check what the yard is screening.

The bag size mistake

The shelf standard is 0.75 cubic feet, which is 36 bags per cubic yard — not 27. Plenty of calculators assume a round 1 cubic foot, and if you order from that figure you arrive 33% short. On a 4×8 bed that is nine bags you have to go back for.

Bags also stop making sense fast. A 4×8 bed at 12 in is 49 bags of the 0.75 cu ft product. Bulk delivery is cheaper and one trip, though most yards have a 1 cubic yard minimum.

Settling

Bed fill drops 10–20% in the first season as air pockets collapse, and a compost-heavy mix can lose 25%. Fill to the top of the boards and expect to top up next spring. This calculator adds the allowance for you.

Do not fill a raised bed with straight topsoil

Iowa State Extension and University of Maryland Extension both make the same point: topsoil alone lacks the permeability and fertility vegetables need. The mixes they describe are around 50% topsoil / 50% compost, or 40 / 40 / 20 topsoil, compost and coarse sand where drainage matters.

Work out your total volume here, then split it by those proportions.

Topdressing a lawn

The hard limit is 1/4 to 1/2 inch per application — that is Penn State Extension's figure, and above it you bury the grass crowns and block photosynthesis. Bare patches will take up to an inch. If you are filling a real dip, do it over several passes across a few weeks rather than one heavy layer. That is the single most common way people kill a lawn while trying to level it.