A cubic meter is a unit of volume, while a tonne is a unit of mass. Thus, the amount of volume required to equal 1 ton of mass depends entirely upon the density of the substance measured. For example, a cubic meter of water at roughly 4 degrees Celsius weighs 1 tonne. A tonne, also known as a metric ton, equals 1000 kilograms, or nearly 2,204 pounds.
A cubic meter of solid stone weighs significantly more than 1 tonne, while a cubic meter of cotton candy hardly weighs anything at all. Even the temperature of the water is important, as water expands as it is either heated or cooled from 4 degrees Celsius.