Topsoil calculator

For a new lawn, spread 100 to 150 mm of topsoil. At 100 mm, one tonne covers about 6.7 m².

  • Updated 20 October 2026
  • Source: Rolawn

For an L-shape, split it into rectangles and add them up.

metres
metres
mm

100–150 mm for lawns, 150–200 mm for borders.

t per m³

Leave as it is unless your supplier gives a figure.

Topsoil needed3.60 tonnes
Bulk bags (1 tonne)
4
Volume
2.40 m³
Area
24.00 m²

6 × 4 m at 100 mm deep, using 1.5 tonnes per m³.

Topsoil settles after spreading, so order a little extra if you need an exact finished level.

How much topsoil per square metre

Using 1.5 tonnes per m³.

DepthPer m²One tonne covers
50 mm75 kg13.3 m²
100 mm (new lawn)150 kg6.7 m²
150 mm (lawn or border)225 kg4.4 m²
200 mm (borders)300 kg3.3 m²
300 mm450 kg2.2 m²

How we calculate this

We multiply the area by the depth to get the volume, then by the weight of a cubic metre of topsoil to get tonnes.

Rolawn says one tonne of standard topsoil is about 0.67 m³, which is about 1.5 tonnes per m³. Wet or heavy soil weighs more, so change the weight if your supplier gives a figure.

Volume (m³) = area × depth (mm) ÷ 1,000Tonnes = volume × 1.5

Questions people ask

How deep should topsoil be for a new lawn?

Rolawn recommends 100 to 150 mm for turf or seed, and 150 to 200 mm for borders and ornamental planting.

How much does a tonne of topsoil cover?

About 6.7 m² at 100 mm deep, or 4.4 m² at 150 mm.

How do I work out topsoil for a raised bed?

Enter the inside length and width of the bed and its depth. Raised beds are often filled with a mix of topsoil and compost, so you may need less topsoil than the total.

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