How Much Topsoil Do I Need?

The depth you order and the depth you want are different

Soil delivered loose is full of air. Spread, watered and walked on, it compacts substantially — and a bed filled level on the day sits noticeably low within a few weeks.

20–25% is normal, which is why the settling allowance here defaults to 20 rather than a token 5.

A 20 × 10 bed at a finished 6 inches means spreading 7.2 inches of loose soil — and ordering 4.44 cubic yards rather than 3.7.

Enter the depth you want to end with. Let the allowance do the rest.

Depth matters far more than area

This is where most of the error lives, and it varies by a factor of forty-eight:

Job	Depth
Topdressing an existing lawn	0.25–0.5 in
Seeding a new lawn	4–6 in
Planting beds	8–12 in
Vegetable / deep-rooted	12 in+

Getting the area slightly wrong costs you a few percent. Getting the depth wrong costs you the whole order.

Topdressing is the one to be careful with. A quarter to half an inch, no more — burying grass kills it, and people reach for "a couple of inches" without thinking.

Measuring the area

Enter the length and width of the bed or lawn. Irregular shapes go in as several rectangles added together — don't use the bounding box of an L-shape, which includes ground you aren't covering.

Curved beds are the awkward case. Unlike edging, where the curve is the thing you're buying, here you want the area inside it — so measuring the containing rectangle and accepting a modest over-order is usually fine. Topsoil tolerates surplus better than most materials, because spare soil always has somewhere to go.

What's worth being precise about is which parts you're actually covering. A bed with established shrubs in it needs soil around them, not over the whole footprint — and people routinely order for the rectangle and then discover half of it has nowhere to go.

Tons or cubic yards — ask before you say a number

Exactly the same trap as buying gravel. Suppliers are split, and the numbers aren't close.

Topsoil density also varies enormously with moisture — dry screened soil runs lighter, wet soil substantially heavier — so it's an input here rather than a fixed constant. Around 1.1 tons per cubic yard is a common figure for screened topsoil.

Ask your supplier two things: which unit they price in, and what density they're using.

Topsoil is not a graded product

Unlike sand or gravel, there's no standard. Quality varies wildly between suppliers — screened or unscreened, sandy or clay-heavy, full of stones or weed seed.

Cheap topsoil that turns out to be subsoil and builders' rubble costs you twice: once to deliver it, and again to remove it. Plus a bed that won't grow anything.

Ask what it is, where it came from, and whether it's screened — before you ask what it costs.

Bags are for small jobs only

The crossover comes sooner than people expect: roughly one cubic yard, which is about 27 one-cubic-foot bags.

Beyond that, bulk is considerably cheaper and it's one delivery instead of several car journeys.

The bag count is shown mainly so you can see the number before deciding bags are the easy option. Our 20 × 10 bed at 6 inches is 120 bags.

Look at the weight before planning the labour

That same bed is 9,778 pounds — nearly five tons.

Wheelbarrows hold less than you think, and the distance from where a lorry can tip to where the soil actually needs to go is what decides whether this is an afternoon or a weekend.

Work that out before the delivery arrives, not while it's sitting on your driveway.

Print the order sheet — the checklist's first three items are all questions to ask the supplier, because the soil itself matters more than the quantity.