Densities and approximate costs of materials

As plastics materials are bought by weight and sold by volume (in the form of moldings) then, any materid with a low density, or specific gravity (SG), has a tremendous advantage. Often therefore, the cost per unit volume is more important than the cost per unit weight. To convert to the cost in cents per cubic inch (c/cu in), multiply the cost per pound (lb) in cents by the SG and then, by 0.0361. Note that, the density in g/cc has the same numerical value as the SG. 

The conversions from one currency to another were obtained by assuming that there are 1.60 dollars to the pound sterling. 

for example, to convert from p/g to c/g multiply the p/g by the currency conversion factor, for example, 1.60 in this case. 

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