Cubic Metres to Tonnes Converter — m³ to Tonnes

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.