1 ct = 200 mg = 0.2g
According to the strict defined parameters of a brilliant cut, it is possible to count the weight also by measuring the basic proportions of a brilliant-cut diamond, e.g. with the diameter (at least two axes perpendicular to each other) and height.
Estimated density [ct] = (girdle circumference) 2 × height × 0,0061.
The carat unit comes from middle age marketplaces where carob seeds were used as a weight unit for trading with precious stones because of their reputation for having a uniform weight.
