Carats to Long Tons (ct to ton (UK))

1 carat equals 1.968413055×10⁻⁷ long tons (rounded).

1 carat = 1.968413055×10⁻⁷ long tons

How to convert carats to long tons

To convert carats to long tons, multiply the number of carats by 1.968413055×10⁻⁷. The factor is rounded to 10 significant digits. To go the other way, multiply long tons by 5,080,234.544.

long tons = carats × 1.968413055×10⁻⁷

Example: 10 carats = 0.000001968413055 long 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)

Long Ton (ton (UK))

Imperial (British)Current unit

2,240 pounds (1,016.05 kg), the imperial or UK ton. Also used for ship displacement.

Before the 15th century an English ton was 2,160 pounds, twenty hundredweight of 108 pounds. Nineteenth-century British definitions included 2,240, 2,352 and 2,400 pounds, though the legal ton was usually 2,240 lb, which is twenty hundredweight of 112 lb. Industry bent the rules: in the 17th and 18th century iron trade, workers were given a 2,240 lb ton of raw material but were expected to return a 2,400 lb ton of processed iron, allowing for waste, and some coal mines delivered long tons but paid miners for a shorter one, which the miners saw as unfair.

The long ton, about 1,016 kg, is within 2 percent of the metric tonne, which makes the two easy to mistake for each other. It is used in the UK, Ireland and most Commonwealth countries that followed the imperial system, although the tonne is now the legal trade unit in the UK, Canada and Australia. Ship displacement has traditionally been quoted in long tons, because a ship cannot be put on a scale and is instead measured by the weight of water it pushes aside. The 2,240 lb figure became the standard for ship design.

1 long ton = 1,016.046909 kilograms (approximately).

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

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