GardenCalcs.uk
Material Weight Calculator — Volume to Weight Conversion
Convert between volume and weight for common garden materials.
Pick the material — the loose bulk density (t/m³) used for the conversion is shown next to each option.
Choose Volume to Weight (m³ → tonnes) or Weight to Volume (tonnes → m³).
Volume of material to convert (m³). Area × depth — e.g. 10 m² at 50 mm = 0.5 m³.
Volume of one bulk bag (default 850L = 0.85m³). Check supplier specs.
Add extra weight for wet material. Wet topsoil can be 15–25% heavier than dry (default 0%).
Extra to order for spillage, spreading losses, or compaction (default 0%). Typical 5–10%.
How We Calculate This
Weight (tonnes) = Volume (m³) × Density (tonnes/m³). Volume = Weight ÷ Density.
Densities are approximate for loose, dry materials. Wet or compacted materials will be heavier — use the moisture allowance to add weight without changing the volume.
Bulk bags assume a standard 0.85 m³ (850 L) builders-merchant bag; change this in the advanced options if your supplier uses 0.5–0.6 m³ bags. Adding a delivery wastage allowance increases the order volume, so the headline bulk-bag count rises to match.
Frequently Asked Questions
Approximately 1.4 tonnes (1,400 kg). This varies with moisture content - wet topsoil can weigh up to 1.7 tonnes per m³.
A standard builders-merchant bulk bag holds about 0.85 m³. Weight depends on the material — at that volume gravel works out around 1.4–1.5 tonnes, MOT Type 1 around 1.8 tonnes, topsoil around 1.2 tonnes and compost around 0.45 tonnes. Adjust the bulk-bag volume in the advanced options if your supplier uses 0.5–0.6 m³ bags.
Many suppliers sell aggregates by weight (tonnes) but quote your project in volume (cubic metres), or vice versa. Knowing the density lets you convert between the two so you order the right amount and can check it fits your access and delivery limits.
Yes — even 1 m³ of gravel or MOT Type 1 is well over a tonne. A standard pickup carries roughly 0.5–1 tonne, a single-axle trailer about 0.75 tonnes, and tipper lorries 10–20 tonnes, so a single cubic metre of dense aggregate can exceed a small trailer or van payload.
Density varies hugely. Per cubic metre, MOT Type 1 is about 2,100 kg, gravel 1,700–1,800 kg, sand 1,500–1,600 kg, topsoil about 1,400 kg, compost about 550 kg and bark mulch about 350 kg. Always check weight when ordering loose delivery.
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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.