GardenCalcs.uk
Topsoil Calculator — How Much Topsoil Do I Need
Calculate topsoil volume in cubic metres, tonnes, and bags.
Length of the bed, border or area to fill, measured along the longest side.
Width of the area at right angles to the length. For an L-shape, split it into rectangles and add the volumes.
Settled depth of topsoil: 10-15cm for new lawns/turf, 15-20cm for borders and beds, 30-40cm for root vegetables (Rolawn).
Leave at 0 to skip costing. Bulk topsoil is typically £25-£50 per tonne plus delivery; bagged is dearer per tonne.
Adds a margin for settling, spillage and uneven ground. Adjust the percentage under Advanced Options.
Extra material to account for waste and spillage
How We Calculate This
Volume is calculated as: Length × Width × Depth (converted to metres).
Weight conversion uses 1.4 tonnes per cubic metre for typical screened topsoil. Actual weight varies with moisture content and composition.
Bulk bags are estimated at 1 tonne each. Small bags are calculated at 25 litres each.
Frequently Asked Questions
Topsoil typically weighs between 1.3 and 1.5 tonnes per cubic metre, depending on moisture content. We use 1.4 tonnes/m³ as a standard estimate.
For new lawns and turf, 10-15 cm is typical. For borders and flower beds, 15-20 cm. For root vegetables, 30-40 cm of quality topsoil is recommended (Rolawn).
Topsoil is the upper layer of natural soil, good for structure. Compost is decomposed organic matter, rich in nutrients. Most gardens benefit from a mix of both.
A standard bulk bag holds approximately 0.7-0.85 m³ and weighs about 1 tonne. Prices vary from £40-£80 per bag depending on quality and delivery distance.
Yes, mixing new topsoil with existing soil is recommended. Dig in or rotavate to blend them together. This avoids a sharp boundary that can impede drainage.
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Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.