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Cubic Metres to Tonnes Converter — m³ to Tonnes
Convert between cubic metres and tonnes for aggregates, sand, soil, and other bulk materials. Uses accurate UK material densities.
Enter the volume of material you need
Weight per bulk bag in tonnes (default 0.85t / 850kg)
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How We Calculate This
This converter uses the density (mass per unit volume) of each material to convert between cubic metres and tonnes. The figures are nominal averages typical of UK bulk materials. Most are loose densities, but the aggregate sub-base figures (MOT Type 1 and hardcore) are quoted at their compacted density, because that is what is normally specified and ordered. Actual bulk density varies with moisture content, compaction and supplier, so confirm the figure with your supplier before ordering.
The formula
Tonnes = Cubic Metres × Density (t/m³)
Cubic Metres = Tonnes ÷ Density (t/m³)
For example, 2 m³ of sharp sand at 1.6 t/m³ = 2 × 1.6 = 3.2 tonnes.
Material densities used
- Topsoil: 1.4 t/m³ (loose)
- Sand (sharp): 1.6 t/m³
- Sand (building/soft): 1.5 t/m³
- Gravel (10-20mm): 1.7 t/m³
- MOT Type 1: 2.1 t/m³ (compacted; loose is lighter at ≈1.8-2.0)
- Hardcore: 1.9 t/m³ (compacted; loose is lighter at ≈1.6-1.9)
- Concrete: 2.4 t/m³
- Ballast: 1.8 t/m³
- Slate Chippings: 1.5 t/m³ (supplier range ≈1.3-1.6)
- Bark Mulch: 0.3 t/m³ (lightweight organic, usually sold by volume, not weight)
All figures are nominal averages. Bulk density changes with moisture, particle size, compaction and source, so treat these as estimates and confirm the actual figure with your supplier before placing an order. MOT Type 1 and hardcore are given at compacted density (the quantity needed once laid and consolidated); if you are converting the weight of loose, as-delivered Type 1, expect roughly 5-10% less per cubic metre.
Bulk bag equivalents
We estimate bulk bags at 0.85 tonnes each by default. This 850kg figure is the industry-standard nominal weight for aggregate bulk bags: sand, gravel, ballast and MOT Type 1 (roughly half a cubic metre per bag). Actual weights vary by supplier and how the bag is filled, so the count is rounded up because you cannot order a partial bag.
Important: lightweight organic materials such as bark mulch are sold by volume, not weight. A bark mulch bulk bag typically holds ≈0.7-1 m³ but weighs only ≈250-350kg, far less than 850kg. For those materials the bulk-bag count shown here is unreliable; order by volume (m³) and use the advanced “Bulk Bag Weight” field to enter the bag’s actual weight if you want a weight-based count.
Frequently Asked Questions
It depends on the type of sand. Sharp sand weighs approximately 1.6 tonnes per cubic metre, while building (soft) sand weighs about 1.5 tonnes per cubic metre. These are approximate densities: actual weight varies with moisture content and compaction. When ordering, always specify whether you want sharp or building sand.
A standard aggregate bulk bag (also called a jumbo bag or ton bag) typically contains approximately 0.85 tonnes (850kg) of material and holds around half a cubic metre. Despite being commonly called 'ton bags', they rarely contain a full tonne. The actual weight depends on the material density and how the bag is filled. This 850kg figure applies to heavy aggregates such as sand, gravel, ballast and MOT Type 1; lightweight materials like bark mulch are bagged by volume and weigh far less. Always confirm the weight with your supplier.
MOT Type 1 is a crushed limestone or granite aggregate used as a sub-base material for driveways, patios, and building foundations. Its compacted density is approximately 2.1 tonnes per cubic metre (the figure this tool uses, because that is what you need once it is laid and consolidated). Loose, as-delivered Type 1 is a little lighter at around 1.8-2.0 t/m³. The name comes from the Ministry of Transport specification for road construction materials.
Bark mulch has a density of only about 0.3 tonnes per cubic metre (ornamental bark is typically 0.25-0.35 t/m³) because it is lightweight organic material with lots of air gaps. A cubic metre weighs just ~300kg, compared to 2,400kg for the same volume of concrete. That matters when working out delivery loads and vehicle payloads. Note that bark and other lightweight materials are sold by VOLUME, not weight: a bark bulk bag usually holds about 0.7-1 m³ but weighs only ~250-350kg, so the 850kg bulk-bag estimate in this tool does not apply to bark. Order it by the cubic metre instead.
Most UK suppliers sell aggregates and sand by the tonne (weight), but you measure the area you need to fill by volume (m³). Use this converter to translate between the two. For example, if you need to fill a 3m³ area with gravel, you will need approximately 5.1 tonnes (3 × 1.7). Always order slightly more than calculated to account for compaction and wastage.
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.