Carat-The Standard Unit of Mass For Gemstones;

The abbreviation for carat is ct.
1ct =0.2 grams
5cts = 1.0 gram
1 grams = 0.035 ounce
1 ounce = 28.35 grams
1 ounce = 141.75cts
Do not confuse carat with karat, the uint of measure of gold purity. Both terms probably originate from the Middle Eastern Word for the seed of the carob tree (in Arabic kharrub). The seeds have a remarkably uniform weight and were used to balance the scales in ancient markets.