Carat Weight

Diamonds are weighed in metric carat. One carat is equal to 100 points, just like one rand is made up of 100 cents. 

Points	Weight in carat
100	1
50	0.50
20	0.20

 
The weight alone does not determine the value of the diamond. A diamond weighing 1 carat can be more valuable than another with the same weight but with better attributes linked to clarity, cut and colour. 

Even though weight is only one of the determinants of value, the tiniest change in weight can make a significant difference in price. Because precision in weight is so crucial to the value and the price, weight is measured to the hundred of thousandths of a carat and rounded to a hundredth of a carat. 

Diamonds that weigh less than 1 carat, are weighed in hundred of a thousand of a carat. Diamonds that weigh more than one carat are measured in carats and decimals. 
 

Diamond weight	< 100	>100
Measurement	Hundred of thousands of a carat	Carats and decimals
Rounded	0.80	1.08 ct
	Zero point eight	One point oh eight carats

 
The carat weight system
 
Diamonds and other gemstones are measured in carat, which is not the same as karat in which the purity of gold is measured. Carat stems from the tiny seeds of the carob tree which have a uniform weight. Early diamond traders used these seeds to balance the scale and the carat metric system was adopted in the early hundreds. One carat is equal to 0.2 grams and 5 carats equals 1 gram.