A mass-derived unit of volume must be defined by reference to the density of some material. In the case of the fluid ounce, this is water. For the cubic ton, the situation is more complex—there are different cubic tons for different materials.
The 1964 Reader's Digest Great Encyclopaedic Dictionary gave the following ton-derived volumes:
- Timber, 40 cubic feet or 480 board feet
- Stone, 16 cubic feet or 0.453 cubic metres
- Salt, 42 bushels
- Lime, 40 bushels
- Coke, 28 bushels
- Wheat, 20 bushels
Converting cubic tons (i.e., volumes) to measures of weight presents difficulties because organic materials such as timber vary in density.
Approximate volume conversions, based on a timber cubic ton of 40 cubic feet:
- 1 ton (40 cubic feet) = 1.133 cubic metres
- 1 cubic metre = 0.883 cubic tons (35.32 cubic feet)
Use by the BBC
The British Broadcasting Corporation (BBC) has used the term cubic tonne on at least three occasions:
- In a television report on greenhouse gases
- In a television report on Silbury Hill
- In an internet article on an Alpine tunnel
The BBC later amended the internet article by changing cubic tonnes to cubic metres.