Bulk Material Density Guide
Density is the bridge between the space a material fills and the weight a supplier may sell. It is also one of the easiest assumptions to misuse.
What bulk density means
Bulk density is the mass of a loose or compacted material divided by the total volume it occupies, including the small voids between particles. If one cubic metre of a material weighs 1.70 tonnes, its bulk density is 1.70 t/m³.
The basic conversion is:
Volume × bulk density = estimated weight
This is different from the density of the solid stone, mineral or soil particles themselves. A pile of gravel contains air gaps, so using the solid-rock density would seriously overstate its delivered weight.
Planning values used on AmountHub
| Material | Typical planning value used by the calculators | Why it can vary |
|---|---|---|
| General gravel | About 1.70 t/m³ | Stone type, grading, moisture and compaction |
| Pea gravel | About 1.60 t/m³ | Particle shape and packing |
| Crushed stone | About 1.75 t/m³ | Grading and fines content |
| Dry sand | About 1.60 t/m³ | Moisture, grading and looseness |
| Damp sand | About 1.70 t/m³ | Water content and packing |
| General topsoil | About 1.30 t/m³ | Organic matter, moisture and texture |
| Dense asphalt mix | About 2.40 t/m³ | Mix design and final compaction |
These figures are deliberately presented as planning assumptions, not universal constants. Supplier or manufacturer data for the exact material should take priority.
Why moisture matters
Water adds mass. Two deliveries of the same sand or soil can therefore have similar volumes but noticeably different weights. Moisture also affects how particles pack. This is why a volume-based supplier quote and a weight-based supplier quote are not always interchangeable using one fixed conversion.
Loose versus compacted material
Compaction reduces the void space between particles. The same mass can occupy more volume when loose and less volume after compaction. For a project that specifies a finished compacted layer, use the required compacted depth and ask the supplier whether a separate compaction or shrinkage factor is needed for delivery.
Do not automatically apply a generic compaction percentage to every material. The correct factor depends on particle grading, moisture, equipment and the target compaction standard.
How to use a supplier density
Suppose your project needs 1.8 m³ of gravel including allowance. AmountHub's general planning density of 1.70 t/m³ gives 3.06 tonnes. If your supplier states that the actual product is 1.82 t/m³, use their figure instead:
1.8 × 1.82 = 3.28 tonnes
The project volume did not change. Only the conversion from volume to weight changed because you obtained better product-specific information.
When volume is more useful than weight
For garden beds, mulch and many bulk landscape products, the job is fundamentally about filling a volume. Weight can be secondary or too variable to be useful. Use volume first when the supplier sells by cubic metre or cubic yard. Use weight when the supplier sells by tonne or ton or when vehicle loading matters.
Common mistakes
- Using solid-rock density instead of bulk density.
- Treating one internet density value as exact for every supplier product.
- Ignoring moisture when converting sand or soil to weight.
- Mixing loose-delivery volume with compacted-finished volume.
- Adding a density allowance and a separate waste allowance without understanding what each represents.
Related calculators
For the broader calculation and rounding policy used across AmountHub, see the methodology page.