Topsoil Calculator: How Much Topsoil Do You Need?

Ordering topsoil in the wrong quantity is an expensive mistake. Too little leaves you short mid-project; too much means paying for material you have to dispose of. The Topsoil Calculator takes the guesswork out of ordering by calculating the exact volume needed for your project and expressing it in bags, bulk bags, or tonnes.

Three project types are supported: garden beds (a standard 20 cm depth is used as default), raised beds (enter your exact depth), and lawn top-dressing (a standard 2–5 cm layer). Multiple bed dimensions can be calculated individually and combined.

Results are given in litres, cubic metres, approximate weight in tonnes, and the equivalent number of 25-litre bags, 50-litre bags, and 850-litre bulk bags (one standard tonne bag). This lets you compare the cost of buying in bags versus bulk delivery.

Topsoil density is assumed at 1,250 kg/m³ for a typical loamy topsoil, which is the standard assumption used by most UK topsoil suppliers for loose-tipped material. Screened and fine topsoil may be slightly less dense; clay-heavy soils may be heavier. Application depths are based on RHS guidelines for bed preparation and lawn establishment.

Enter the length and width of your area in metres, select your project type, and adjust the depth if needed. The calculator returns volume in litres and m³, weight, and bag equivalents. Use the bag counts to compare the cost of retail bag purchases against ordering a bulk delivery — for most projects over 1 m³, bulk delivery is significantly more economical.