There are two significant weights to consider when comparing Carbon Fibre with Steel and Aluminium: the weight of a material’s volume, measured in kg per cubic meter (or pounds per cubic foot) – specific gravity, and its weight relative to another substance.
For example, steel has a density of 7850 kg/m^(x), and aluminium is 7000kg/m^(x).
The average carbon fibre density is 2000-3000kg/m^(x).
This means that for every volume unit or pound unit of steel, there will be fewer units needed for Carbon Fibre.