The conversion
tonnes = cubic metres × bulk density (t/m³). For example, 20 m³ of crushed rock at 1.60 t/m³ is about 32 tonnes.
These are loose, stockpiled densities, not compacted. Moisture can add 10 to 20% for aggregates and much more for mulch, so weigh a load if the number matters.
Stockpile densities for 16 materials
Typical values, compiled from earthwork reference tables and supplier data. These are the same figures the Stockpile app uses.
| Material | Typical t/m³ | Usual range |
|---|---|---|
| Crushed rock / road base | 1.60 | 1.45–1.85 |
| Crusher dust / screenings | 1.70 | 1.55–1.90 |
| River gravel (rounded) | 1.60 | 1.50–1.70 |
| Rail ballast | 1.55 | 1.45–1.65 |
| Recycled crushed concrete | 1.45 | 1.30–1.60 |
| Reclaimed asphalt (RAP) | 1.55 | 1.40–1.70 |
| Decorative pebble | 1.55 | 1.45–1.65 |
| Sand (dry) | 1.50 | 1.40–1.60 |
| Sand (damp / wet) | 1.80 | 1.70–2.00 |
| Topsoil (loose stockpile) | 1.30 | 1.20–1.40 |
| Fill dirt / subsoil | 1.60 | 1.50–1.75 |
| Clay (common) | 1.70 | 1.60–1.85 |
| Garden / landscape mix | 1.00 | 0.90–1.10 |
| Wood chip mulch | 0.30 | 0.20–0.40 |
| Bark mulch | 0.40 | 0.35–0.50 |
| Compost (screened) | 0.70 | 0.50–0.80 |
Getting a better tonnage
Two things move the answer most: the volume itself and the density you use. Measuring the real surface fixes the first. For the second, calibrate against weighbridge tickets: divide the tonnes on a ticket by the measured volume of the same load, and use that density for that material.
The Stockpile app lets you pick any of these materials or enter your own density, and shows tonnes beside the volume on every scan.
Frequently asked questions
How many tonnes in a cubic metre of gravel?
About 1.6 tonnes for crushed rock or river gravel in a loose stockpile, usually between 1.45 and 1.85.
How many tonnes in a cubic metre of sand?
About 1.5 tonnes dry and 1.8 tonnes damp.
How many tonnes in a cubic metre of topsoil?
About 1.3 tonnes for loose stockpiled topsoil.
Get the volume right first.
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