Carats to Grams Converter

How it is calculated

The converter uses the metric carat, defined as exactly 0.2 g: g = ct × 0.2 and mg = ct × 200, where ct is the stone's weight in carats. Grams are shown to four decimals and milligrams to two, which matches how gem weights are usually reported (to the hundredth of a carat, or 2 mg). It converts weight, not size or value: two stones of the same carat weight can look different in diameter depending on the material and cut. Negative values are converted the same way, and decimals must use a point, not a comma. This is the carat of mass, not the karat that states gold purity out of 24.

Common mistakes

• Mixing up carat (ct) with karat (K). A 2.35 ct stone is a weight; 18K gold is a purity of 18/24, and the two do not convert to each other.
• Dividing by 0.2 when you wanted to go from carats to grams. Carats to grams multiplies by 0.2; grams to carats is the one that multiplies by 5.
• Reading 0.4700 g as 470 g. The result is below half a gram, so check the unit label and the decimal point.
• Assuming equal carat weight means equal size. Different gem materials have different densities, so the same carat weight does not give the same dimensions.