Convert Carats to Kilograms

About converting Carats to Kilograms

Carats (ct) and Kilograms (kg) are both units of weight & mass, so converting between them is a single multiplication: multiply your Carats figure by 0.0002. Ten Carats comes to 0.002 Kilograms, and a hundred works out at 0.02 Kilograms.

Rule of thumb: going from Carats to Kilograms divides, so the figure always shrinks — it takes about 5,000 Carats to make a single Kilogram. If your answer came out bigger, you have the conversion the wrong way round.

What is a Carat?

The metric carat is 0.2 grams exactly, standardised early in the twentieth century to replace a tangle of local carats that differed from one gem market to the next. Its name is traditionally traced to the carob seed, once used as a counterweight for small valuables. The trap is the near-identical karat, which is not a mass at all — it measures gold purity in twenty-fourths, so 18-karat gold is eighteen parts gold to six of other metal. Jewellers also split the carat into 100 points, which is why a "fifty-point" diamond is simply half a carat.

What is a Kilogram?

The kilogram was the last SI unit still defined by a physical object — the International Prototype Kilogram, a platinum-iridium cylinder kept in a vault near Paris since 1889. The problem was that it drifted. Careful comparisons against its official copies showed the masses diverging by tens of micrograms, and because the prototype simply was the kilogram by definition, there was no way to say which side had changed. In 2019 it was redefined in terms of the Planck constant, so any properly equipped lab can now realise a kilogram from physics rather than from an artefact.

To put both in perspective: a typical engagement-ring diamond weighs about one carat, while a liter of water weighs about a kilogram.

The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Kilograms to Carats converter, or browse all Weight & Mass converters.