# Carats to Kilograms (ct to kg) Source: https://www.unitconvertercalculator.com/weight/carats-to-kilograms/ **1 ct = 0.0002 kg** One carat equals exactly 0.0002 kilograms (two ten-thousandths of a kilogram). The kilogram is the base unit of mass in the International System of Units, while the carat is a specialized gemstone unit. At 5,000 carats per kilogram, this conversion is essential for gemstone trade logistics, customs declarations, and insurance valuations where standard metric weight is required. ## Formula Apply the conversion factor ## Conversion Table | Carats (ct) | Kilograms (kg) | |---|---| | 1 ct | 0.0002 kg | | 5 ct | 0.001 kg | | 10 ct | 0.002 kg | | 50 ct | 0.01 kg | | 100 ct | 0.02 kg | | 500 ct | 0.1 kg | | 1000 ct | 0.2 kg | | 2500 ct | 0.5 kg | | 5000 ct | 1 kg | | 10000 ct | 2 kg | | 25000 ct | 5 kg | | 50000 ct | 10 kg | | 100000 ct | 20 kg | | 500000 ct | 100 kg | ## Units ### Carat (ct) A carat is a unit of mass equal to exactly 200 milligrams (0.2 grams), used for measuring gemstones and pearls. Adopted internationally in 1907 by the Fourth General Conference on Weights and Measures. ### Kilogram (kg) The base unit of mass in the International System of Units (SI). Equal to 1000 grams. Used worldwide for everyday weighing and commerce. ## Background The Cullinan Diamond, the largest gem-quality rough diamond ever found, weighed 3,106.75 carats - just 0.621 kilograms, barely more than half a kilogram. Even the most spectacular diamonds are remarkably light in kilogram terms. A wholesale gemstone dealer might handle hundreds of thousands of carats annually, but the total physical weight in kilograms would fit in a few small bags. ## Good to Know The kilogram was redefined in 2019 based on the Planck constant, replacing the physical platinum-iridium cylinder that had served as the standard since 1889. This change had no practical effect on the carat-to-kilogram conversion, but it meant that for the first time in history, both units - the carat (defined metrically since 1907) and the kilogram - are based on fundamental physical constants rather than physical artifacts. ## FAQ ### How many carats are in one kilogram? One kilogram equals exactly 5,000 carats. This comes from 1 carat being exactly 0.2 grams and 1 kilogram being 1,000 grams: 1,000 divided by 0.2 equals 5,000. ### Why do gemstone traders need the kilogram conversion? International shipping, customs duties, and insurance policies require weight in kilograms. A gem dealer might describe inventory as '2,500 carats of sapphire' internally, but customs paperwork needs '0.5 kg' for tariff calculations and freight pricing. ### What is the heaviest diamond ever found in kilograms? The Cullinan Diamond, found in South Africa in 1905, weighed 3,106.75 carats or about 0.621 kg. It was cut into several major gems, the largest being the Great Star of Africa (530.2 carats, about 0.106 kg), which is set in the British Sovereign's Sceptre. ## Non-Frequently Asked Questions ### How much would a kilogram of diamonds cost? One kilogram is 5,000 carats. The price depends wildly on quality: 5,000 carats of industrial-grade diamonds might cost a few hundred thousand dollars, while 5,000 carats of flawless D-color brilliant-cut stones would be worth billions - far more than anyone has ever assembled in one place. ### Could I carry a million carats of diamonds? One million carats equals exactly 200 kilograms. That is roughly the weight of a large refrigerator. You could not carry it, but you could roll it on a cart. At even modest quality, this cart would be worth more than most countries' GDP. You would want very good insurance and a very strong lock. ### Does a kilogram of diamonds weigh the same as a kilogram of feathers? Yes, both weigh exactly one kilogram. But the diamonds would occupy much less space because diamond has a density of about 3.52 g/cm cubed, while feathers are mostly air. A kilogram of loose feathers would fill a large pillow; a kilogram of diamonds would fit in a coffee mug. ## Related Articles - [Why We Measure: The Deepest Urge in Human Civilisation](https://www.unitconvertercalculator.com/blog/why-we-measure) - [The Map Is Not the Territory: Why Every Measurement Is Wrong](https://www.unitconvertercalculator.com/blog/the-map-is-not-the-territory) - [Zero: The Most Dangerous Number in Measurement](https://www.unitconvertercalculator.com/blog/zero-the-most-dangerous-number-in-measurement) - [The Kilogram Problem: The Object That Was Its Own Definition](https://www.unitconvertercalculator.com/blog/the-kilogram-problem) - [The Body as a Ruler: Every Measurement Unit That Came From Us](https://www.unitconvertercalculator.com/blog/the-body-as-a-ruler) - [Why Your Recipe Is Lying to You: The Chaos of Cooking Measurements](https://www.unitconvertercalculator.com/blog/why-recipe-measurements-are-unreliable) - [15 Obscure Measurement Units You've Never Heard Of (But Still Need)](https://www.unitconvertercalculator.com/blog/obscure-measurement-units-guide) - [When Measurements Go Wrong - Disasters, Blunders and Happy Accidents](https://www.unitconvertercalculator.com/blog/when-measurements-go-wrong) - [The Surprising Stories Behind Everyday Units of Measurement](https://www.unitconvertercalculator.com/blog/stories-behind-measurement-units) - [Metric vs. Imperial - The Complete Guide to the World's Two Measurement Systems](https://www.unitconvertercalculator.com/blog/metric-vs-imperial-complete-guide) - [Understanding Weight Units - Kilograms, Pounds, Stones & Ounces](https://www.unitconvertercalculator.com/blog/understanding-weight-units) - [Complete Baking Measurement Guide - Cups, Grams, Ounces](https://www.unitconvertercalculator.com/blog/baking-measurement-guide) ## See Also - [Kilograms to Carats](https://www.unitconvertercalculator.com/weight/kilograms-to-carats/)