Topsoil Calculator (UK)
Last updated: 12 August 2026
Work out how much topsoil you need for a lawn, border or raised bed. Enter your area and depth and get cubic metres, tonnes and bulk bags.
How the calculation works
Volume = area × depth. We convert to tonnes using the bulk density of your soil type — screened topsoil is about 1.55 t/m³, while compost-rich blends are lighter and unscreened as-dug soil is heavier and wetter.
Above roughly 8–10 bulk bags, a loose tipper load is almost always cheaper per tonne, provided you have access and somewhere to tip it.
How deep should topsoil be?
| Use | Depth | Per m² |
|---|---|---|
| Levelling an existing lawn | 25–50mm | 0.04–0.08 t |
| New lawn from turf or seed | 100–150mm | 0.15–0.23 t |
| Flower and shrub borders | 250–300mm | 0.39–0.47 t |
| Raised vegetable beds | 400mm+ | 0.62 t+ |
Choosing topsoil
Look for BS 3882 compliant screened topsoil for lawns — it is graded, weed-suppressed and free of stones and debris. Cheap unscreened soil often arrives full of builders rubble and perennial weed root, and the cost of picking that out exceeds what you saved.
Frequently asked questions
How much topsoil do I need per square metre?
At 100mm deep, about 0.155 tonnes (155kg) per square metre. So a 50 square metre lawn needs roughly 7.8 tonnes, or about 10 bulk bags.
How many square metres does a bulk bag of topsoil cover?
A typical 850kg bulk bag covers about 5.5 square metres at 100mm deep, 11 square metres at 50mm, or 2.2 square metres at 250mm for a border.
How deep should topsoil be for a new lawn?
100mm of good screened topsoil is the standard for a new lawn, increasing to 150mm over poor or compacted ground. Less than 100mm and the grass struggles to root through dry spells.
Is it cheaper to buy topsoil in bulk bags or loose?
Loose tipper loads are usually significantly cheaper per tonne once you need more than about 8 to 10 bulk bags, provided you have vehicle access and somewhere for it to be tipped.
What is BS 3882 topsoil?
BS 3882 is the British Standard for topsoil quality. Compliant soil is screened, tested for contaminants and nutrients, and free from significant weed and debris — worth specifying for lawns and planting.
Related calculators
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How many rolls of turf for your lawn, plus topsoil.
Gravel Calculator
Gravel, shingle and chippings in tonnes and bulk bags.
Aggregate Calculator
MOT Type 1, gravel, sand or topsoil — tonnes and bulk bags.
Estimates are for guidance only. Material dimensions, densities and coverage vary by supplier — always confirm quantities before ordering, and consult a qualified professional for structural work.