Topsoil settles once it is watered, and it is heavier wet than dry — so the volume you spread is not the volume you order, and the tonnage you are quoted is not always the material you get. This does both, and tells you where subsoil should be doing the job instead.
For beds, borders, lawns and levelling. Enter the area and the finished depth you want, and get the amount to order with settlement already allowed for.
Works in metric and US imperial — you choose at the start and can switch at any time. Every figure this calculator uses is published with its source, and the result comes with a printable order sheet. No account, no email, and nothing you type leaves your browser.
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All calculators · How to use them · The standards behind our figures
Area × the finished depth you want, plus a settlement allowance of around 20%, converted at 1,400 kg/m³ for screened topsoil. Soil settles once it is watered and walked on, and most of that happens in the first month — so the volume you spread is not the volume you order. The allowance is settlement, not waste, and it is already applied.
A 10 m² bed at 150 mm finished is 1.5 m³ in place, so about 1.8 m³ to order — roughly 2.5 tonnes. In bulk bags at a declared minimum fill of 800 kg that is four bags, not two and a half. This is where topsoil orders go wrong more often than on the depth.
BS 3882:2015 caps spread topsoil at 300 mm / 12 in. Below that, the standard expects loosened subsoil to BS 8601:2013 — not more topsoil. That matters because deep topsoil is expensive and no better: what roots need underneath is a rootable layer, not a richer one. Subsoil should be loosened rather than just tipped, or it becomes a pan that water sits on. The standard is summarised here.
For beds and borders, 150 mm is a normal working depth and BS 3882:2015 caps spread topsoil at 300 mm. Deeper than that the standard expects loosened subsoil to BS 8601:2013 rather than more topsoil — roots need a rootable layer underneath, not a richer one.
No, and it may not even be a fixed size. Suppliers who declare a volume sell around 750 litres (0.75 m3). Merchants who declare a weight sell a bag with a minimum fill of around 800 kg. Convert your tonnage into bags rather than assuming one bag is one tonne.
No, not as a substitute. A pure compost or garden-mix bed will drop noticeably in its first season and can be too rich for many plants. Compost belongs mixed into topsoil or spread as a surface layer, not used as the body of the soil.
It is the weakest figure on this page and we would rather say so. We use 1,400 kg/m3 for screened topsoil, but published figures vary widely because topsoil is a natural material whose weight depends on its organic content and how wet it is. If your supplier quotes a figure, use theirs.