Conversion for mass

The unit of mass is the kilogram. The kilogram is one of the seven base units of the SI system of units. All other units are derived from the base units. In the 18th century, the kg was defined as the mass of one cubic decimeter of water. Since 1898, the kg has been equal to the mass of the international prototype. This is made of platinum-iridium and is stored in Paris.

In Great Britain (UK) and the United States of America (US) the avoirdupois system (avdp system) is common:
1 Pound [lb] = 16 Ounces [oz] = 256 Drams [dr] = 7000 Grains [gr]
1 Short Ton [tn] = 2000 Pounds [lb]
1 Long Ton [l.tn] = 2240 Pounds [lb]
1,0 Pound [lb] = 0,45359237 Kilogramm [kg]

The Troy system is preferably used for gold, silver and precious stones.
1 Troy Pound [lb]= 12 Troy Ounces [oz] = 240 Pennyweights [pwt] = 5760 Grains [gr]
1,0 Pound [lb] = 0,3732417216 Kilogramm [kg]

The carat [ct] is the unit of weight for gemstones. It was derived from the weight of a carob tree seed.
In the Troy system, 1 carat = 0.2053 grams.

The metric carat [ct] was introduced in 1875:
1 Carat [ct] = 0,2 Gramm [g]

The gold carat [kt] is an indication of precious metal alloys. The “Cologne Mark” (233.8g) was divided into 24 parts (carat) for gold and 16 parts (loth) for silver.
14 kt gold is 14 parts of precious metal out of a total of 24 parts, so 14/24 = 0.583. Instead of 24 parts, today we calculate in 1000 parts. 14 kt gold content corresponds to 585/1000 gold content.

The "Hundredweight" [Cwt], which is no longer in use, corresponds approximately to the "hundredweight" or the "quintal" in Europe. In Great Britain, 112 pounds avoirdupois (50.8023 kg) is a "Hundredweight" or "Long Hundredweight". 20 "Long Hundredweights" correspond to one "Long Ton". In the United States, however, a good equivalent to the hundredweight was abandoned in favor of the decimal system. Here, 100 pounds avoirdupois (45.3592 kg) is a "hundredweight", also known as a "short hundredweight" or "cental". 20 centals equals one “short ton”.