Carats to Metric Tons (ct to t)

1 carat equals 2×10⁻⁷ metric tons exactly.

1 carat = 2×10⁻⁷ metric tons

How to convert carats to metric tons

To convert carats to metric tons, multiply the number of carats by 2×10⁻⁷. This factor is exact. To go the other way, multiply metric tons by 5,000,000.

metric tons = carats × 2×10⁻⁷

Example: 10 carats = 0.000002 metric tons.

About these units

Carat (ct)

Metric (SI)Current unit

Exactly 200 milligrams. The unit for weighing gemstones such as diamonds. Not to be confused with the karat, a measure of gold purity.

Jewellers once weighed stones against seeds. The word carat traces back to the Greek keration, meaning a carob seed, and reached English through Italian and Arabic. Carob seeds were used as balance weights for gems and gold, though their mass varies about as much as any seed does. Before 1907 each country had its own carat, ranging from roughly 187 to 216 milligrams. It was used for gold early on and for diamonds from the 1570s. An international carat of 205 mg was proposed in Paris in 1871, but the 200 mg metric carat won out.

The metric carat was adopted at the Fourth General Conference on Weights and Measures in 1907. France made it mandatory, the United States followed in 1913 and the United Kingdom in 1914. Today it is exactly 200 mg, so five carats make a gram, and it is divided into 100 points of 2 mg each; a diamond described as 25 points is a quarter carat. Carat is used for gemstones and pearls, and it should not be mixed up with karat, which measures the purity of gold and is a separate idea.

1 carat = 0.0002 kilograms (exactly).

Sources: Wikipedia: Carat (mass); NIST Guide to the SI, Appendix B.8 (mass conversions)

Metric Ton (t)

Metric (SI)Current unit

1,000 kilograms (about 2,204.6 lb), also spelled tonne. Used for cargo, grain and vehicle weights outside the US.

Barrels gave the tonne its name. The word goes back to a Germanic root for a large cask, the tun, and a full tun could easily weigh around a tonne. In English this became ton; the spelling tonne has been used in France since 1842, where it replaced the older tonneau, and pre-metric French tonnes were 2,000 livres, about 979 kg. Once the metric system took hold, the tonne was fixed at 1,000 kilograms, which is the mass of roughly a cubic metre of water.

The unit is accepted for use with the SI, and its symbol is a lowercase t with no period. Because it sits close to the old English ton, the two get confused: the short ton used in the US is about 10 percent lighter than a tonne, while the long ton differs by less than 2 percent. NIST calls the unit the metric ton, and the spelling tonne is rare in the US. Very large quantities are stated in prefixed forms such as the megatonne, which equals a teragram. In explosives, a tonne of TNT is taken as about 4.2 gigajoules.

1 metric ton = 1,000 kilograms (exactly).

Sources: Wikipedia: Tonne; Wikipedia: Ton; NIST Guide to the SI, Appendix B.8 (mass conversions)

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