Convert from obol, obolos, obolus [Greece] to carat [international]

Unit Definition (obol, obolos, obolus [Greece])
The obol, obolos, obolus [Greece] is a historic unit of weight or mass. The obol is a very small weight that originated as the weight of a tiny Greek coin. In modern Greece, the obolos is an informal name for the decigram (0.1 gram).

Unit Definition (carat [international])
The carat [international] is a unit of mass used for diamonds and other precious stones. Originally spelled karat, the word comes from the Greek keration, a carob bean; carob beans were used as standards of weight and length in ancient Greece in much the same way barleycorns were used in old England. Traditionally the carat was equal to 4 grains. The definition of the grain differed from one country to another, but typically it was about 50 milligrams and thus the carat was about 200 milligrams.