Specific gravity. When describing this measurement unit of a cargo, liquid cargo is measured in “S.G.” or “Specific gravity”.
This is the reverse of S.F., being the mass (or “weight”) of one unit of volume of the liquid expressed as a ratio to the ‘mass per unit volume of pure water. S.G. has no units and is simply a number. For example, the corrected S.G. of one type of crude oil can be expressed as 0.835. This means that it would also weigh 0.835 tonnes per cubic metre. The word “corrected” refers to the difference between the densities as measured at the existing temperature and that of the oil measured at a standard temperature. (See also S.F. for measurement units for dry cargo.)