How much topsoil do I need?

Multiply the area by the depth to get the volume in cubic metres, then multiply by the density for tonnes. Topsoil is roughly 1.3 tonnes per cubic metre, though garden mixes are lighter. The calculator works out both.

How deep should topsoil be?

For a new lawn, around 100 to 150 mm of good soil gives roots room to grow. Garden beds often want more. Enter the finished depth you want in millimetres.

Is topsoil sold by volume or weight?

Bulk topsoil is usually sold by the cubic metre, while some suppliers quote tonnes. The calculator shows both so you can order in whichever unit your supplier uses.

Topsoil Calculator

This calculator works out how much topsoil or garden mix to order for a lawn, garden bed or landscaping job, converting the area you are covering into both a volume and a weight so you can order confidently, whichever unit your supplier quotes in. You enter the area in square metres, the finished depth you want in millimetres, and the density in tonnes per cubic metre, which defaults to 1.3 for standard topsoil but can be adjusted lower for a lighter garden mix or higher for a heavier clay-based soil. The calculator instantly returns the volume needed in cubic metres and the equivalent weight in tonnes, updating as you change any figure. For example, a 25 square metre lawn topped up 100 millimetres deep needs 2.5 cubic metres of topsoil, or about 3.25 tonnes at the default density. Use it before ordering bulk soil so you are not caught short partway through a job, and remember that soil settles once spread and watered in, so order a little extra for a level finish. If your supplier has given you a density figure, enter that instead of the default for a more accurate result. This is a planning estimate based on the figures you enter; actual quantities can vary with compaction and moisture content, so treat the result as a guide rather than an exact order quantity.

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Area (m²)

Depth (mm)

Density (tonnes per m³)

0 m³

topsoil needed

Tonnes0 t

Soil settles, so order a little extra for a level finish.

How it works

The volume is the area times the depth in metres. Multiply by the density to get the weight. Topsoil is around 1.3 tonnes per cubic metre, while light garden and compost mixes weigh less. Use the figure your supplier gives if you have it.

Worked example

For a 25 square metre lawn at 100 mm deep, the volume is 2.5 cubic metres. At 1.3 tonnes per cubic metre that is about 3.25 tonnes of topsoil.

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Cubic Metre Calculator: work out a volume.

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