How much does a cubic metre of topsoil weigh?

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.

How deep should topsoil be?

For new lawns, 10-15 cm is typical. For flower beds, 20-30 cm. For vegetable gardens, at least 30 cm of quality topsoil is recommended.

What is the difference between topsoil and compost?

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.

How much is a bulk bag of topsoil?

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.

Can I mix topsoil with existing soil?

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.

GardenCalcs

Topsoil Calculator — How Much Topsoil Do I Need

Calculate topsoil volume in cubic metres, tonnes, and bags.

Length

Width

Depth

Price per Tonne (optional)

Include 10% wastage

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

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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.