How Much Topsoil Do I Need? A UK Guide

The calculation is straightforward: volume (m³) = area (m²) × depth (m). Keep everything in metres and the arithmetic is simple — a 10 m² bed at 150 mm (0.15 m) needs 1.5 m³ of topsoil.

The confusion usually comes from the fact that topsoil is sold in at least three formats: loose by the cubic metre or tonne, bulk (dumpy) bags of roughly 0.6 m³ each, and small handy bags of 25–40 litres. The volume figure you calculate is the same in every case — it's just the unit you order in that changes.

Takeaway: get the area and depth right in metres and the rest is arithmetic.

The depth you need depends entirely on what you're growing into it. Getting this wrong is expensive — too shallow and grass struggles in dry spells, too deep and you're paying for soil that does nothing useful.

Here are the standard UK depth ranges for common jobs:

For a new lawn, 100–150 mm over firmed, levelled ground is the sweet spot. Less than that and the turf or seed will desiccate in a dry summer; more and you're spending money you don't need to. Raised beds and vegetable plots need 300–400 mm to give root crops room — but that depth is often blended with compost rather than pure topsoil.

Takeaway: for a new lawn, 100–150 mm over firmed ground is enough; deeper wastes money, shallower and the grass will struggle.

A homeowner in Rochdale is laying a new lawn over an area of 8 m × 5 m at 100 mm depth.

Area = 8 × 5 = 40 m². Depth = 0.10 m. Base volume = 40 × 0.10 = 4.0 m³. Add 10% for settling: 4.4 m³. At 1.5 tonnes per m³, that's approximately 6.6 tonnes. At 0.6 m³ per bulk bag: 8 bulk bags (4.4 ÷ 0.6 = 7.33, rounded up).

A lawn this size is almost always cheaper to order as a loose delivery rather than bagged — you'd need 8 dumpy bags which, at £60–£80 each, adds up quickly. A loose 7-tonne delivery from a local supplier will typically undercut that, though you'll need somewhere to tip it.

Use the topsoil calculator to change the dimensions and get your own figures.

Takeaway: for a lawn this size, order the full tonne — a part-tonne top-up delivery rarely saves money once you factor in the second delivery charge.

Three raised beds, each 2 m × 1 m, filled to 300 mm depth.

Total area = 2 m² × 3 beds = 6 m². Volume = 6 × 0.3 = 1.8 m³. Add 10%: ~2.0 m³. That's approximately 3 tonnes or 4 bulk bags (2.0 ÷ 0.6 = 3.33, rounded up).

The important caveat for raised beds: at 300 mm you rarely fill the full depth with pure topsoil. Most UK gardeners blend the lower 100–150 mm with composted bark or a peat-free multi-purpose compost, which improves drainage and saves money. If you're blending, the topsoil volume you actually need could be closer to 1.2–1.4 m³.

Takeaway: for raised beds, blend in compost from the bottom and you'll need less pure topsoil than the full-depth figure suggests.

One cubic metre of screened topsoil weighs approximately 1.5 tonnes. This varies — wetter or clay-heavy soil is heavier, lighter sandy soils less so — but 1.5 t/m³ is the figure British suppliers generally quote for screened multipurpose topsoil and it's a reliable working number.

A typical UK bulk (dumpy) bag holds 0.6 m³ (~900 kg or ~0.9 tonnes), though bag volumes vary between suppliers. One 0.6 m³ bag covers roughly 6 m² at 100 mm depth or 12 m² at 50 mm depth. Always confirm the bag volume with your supplier before ordering by bag count, because 'a bulk bag' is not a standard size and some bags are 0.5 m³ or 1.0 m³.

Takeaway: always confirm bag volume with the supplier before ordering by bag count — 'a bulk bag' isn't a fixed size.

Loose screened multipurpose topsoil typically costs £30–£45 per tonne delivered in 2026, though this varies significantly by region and load size. Small loads under 5 tonnes usually carry a delivery surcharge that can equal or exceed the soil cost itself — so ordering marginally more to hit a minimum load size often makes financial sense.

Bagged topsoil runs considerably more per cubic metre. Bulk bags at Travis Perkins or Jewson typically cost £55–£85 each depending on grade and location. Specialists like Rolawn supply premium grade topsoil to BS 3882 in both bags and bulk, and are worth comparing for larger garden jobs where quality matters.

The contrarian point most guides skip: bagged topsoil almost always costs more per cubic metre than a loose delivered load. Above roughly 2–3 m³, a loose tipped delivery wins on price — but you need somewhere to tip it, a way to barrow it into place, and the willingness to shift a few tonnes of soil yourself.

Takeaway: above 2–3 m³, price a loose delivery alongside bags — the saving is usually substantial, but only works if you have clear access for the lorry.

BS 3882:2015 is the UK specification for topsoil. It defines three grades: multipurpose, specific purpose and economy. For lawns and general landscaping, multipurpose grade is the standard choice — it's tested for nutrient levels, organic content, pH, and absence of contaminants.

Economy grade is cheaper but can carry more stones, weed seeds, roots and debris. It might be fine for filling a bank where aesthetics don't matter, but it's a poor choice for a lawn you're about to turf or seed. Always ask the supplier to confirm which grade they're quoting — 'topsoil' on a price list doesn't tell you anything without the grade.

Takeaway: ask for multipurpose grade to BS 3882 by name — don't assume 'topsoil' on a price list means the same thing everywhere.

Most people order to their calculated volume and end up short. The reason is simple: freshly tipped topsoil is loose and fluffy, and it compacts by roughly 10–20% once it's spread, walked on and watered in. Order exactly to the calculation and you're almost certainly going to be a few barrowloads light when you level off.

A groundworker I spoke to said his habit is to round a lawn-sized order up by a full tonne, because a second small top-up delivery almost always costs more in delivery charges than the extra soil does. On his maths: paying an extra £35 for a tonne you might not fully use beats paying £45–£60 to get a lorry back out.

That's exactly why the topsoil calculator defaults to a 10% wastage allowance — not because you'll literally waste 10%, but because the combination of settling, levelling losses and the occasional barrowload that goes over the fence means ordering 10% over is almost always the right call.

Takeaway: build in at least 10% over your calculated volume — settling and levelling will use most of it, and a top-up delivery almost always costs more than just ordering right the first time.

Enter your area dimensions, depth, and wastage allowance and the calculator shows you cubic metres, litres, tonnes and bulk bags in one step. It handles rectangular and circular areas and lets you switch between metres, feet and centimetres.

In summary: multiply area by depth in metres, add 10%, check the grade (BS 3882 multipurpose for most jobs), and price both loose and bagged before deciding. The calculator handles the arithmetic — the rest is a five-minute call to your local supplier.