How to Use the Carat to Gram Converter
Diamonds and gemstones aren't weighed in grams — they use a special unit called the carat (ct). The word "carat" originally came from the weight of carob tree seeds, but in 1907 the International Committee for Weights and Measures fixed it at exactly 1 carat = 0.2 grams (200 milligrams), and that metric standard is now used worldwide. This calculator instantly converts between carats, grams, milligrams, and ounces based on the value you enter.
If you know the carat weight of a diamond in a ring or necklace, you can quickly see what that means in grams. A 1-carat diamond weighs just 0.2g, but price per carat rises exponentially as size increases, so accurate unit conversion matters when reading a gem appraisal or quote.
Key Carat Conversion References
- 1 carat (ct) = 0.2g = 200mg
- 1g = 5ct
- 1oz = 28.3495g ≈ 141.7ct
Note that a gemstone carat (ct) and gold karat (K) are completely different concepts. The K used for 14K, 18K, and 24K gold refers to metal purity (alloy ratio), and has no relation to the ct weight unit this calculator handles — don't confuse the two.
Frequently Asked Questions
1 carat equals exactly 0.2 grams (200 milligrams). This metric carat standard was internationally adopted in 1907 and is used worldwide.
No. A gemstone carat (ct) measures weight, while gold karat (K) measures purity. This tool converts the weight unit ct, not gold purity.
1 gram equals 5 carats. So five 1-carat gemstones together weigh exactly 1 gram.