How to Calculate Gemstone Weight
Worldwide the standard unit used for weighing diamonds and gemstones is the metric carat. It takes its name from the carob seeds, these seeds have a fairly uniform size and were used by early gem traders as counterweights in their balance scales.
The modern metric carat was adopted by the internationally in 1913 and today a carat weighs exactly the same in every corner of the world.
Do not confuse Carat with Karat which refers to the purity of gold.
One carat is equal to 200 milligrams or 1/5th of a gram. It can be further subdivided into 100 points or Cents. For example, a 50-points diamond weighs 0.50 carats.