Internationally Gems are generally weighted in CARATS. Carat being a measure of weight which means on metric scale 200 milligrams. This is a standard system and is recognized worldwide.
However, in India, though for business dealings carat is being used, but for retail sales the traditional concept of ‘RATTI’ is still in use. Ratti is approximately 182 milligrams. In few areas 120 milligrams is said to be a Ratti. (so a ratti can be 0.9 carat or 0.6 carat depending on where do u live)
Similarly the Bigah (length) and cents (area) vary from state to state… and worse a lot of the government’s land records are in these unstandardized units of measurement… Why does not ISI (Indian Standards Institute) goes ahead and standardizes these units… or abolish it… lest they create confusion.
BTW guys you might also like Carl Sagan’s audio documentary Pale Blue Dot