Convert Milligram to Carat (mg → ct)

Converting milligrams to carats is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in milligrams

   Start with the number of milligrams (mg) you want to convert.
2. 2
   Multiply by 0.005

   The conversion factor from mg to ct is 0.005. Multiply your value by this number.
3. 3
   Read the result in carats

   The result is your value in carats (ct).

Multiply the value in milligrams by 0.005. For the reverse direction, multiply by 200.

• ✓1 mg = 1/1000 g = 1,000,000 µg. Always check which prefix the label uses.
• ✓Read medication labels carefully — confusing mg and µg can be a 1000× dosing error.
• ✓Nutrition labels list minerals in mg and vitamins (A, D, K) in µg.

• ✗Reading 500 mg as 500 g on a medicine bottle — a potentially fatal 1000× error.
• ✗Confusing mg (milligram) with mg/kg (dose per kilogram of body weight).
• ✗Mixing up mg and µg — µg is 1000× smaller.

What is the Milligram?

The milligram equals one thousandth of a gram (0.001 g) or 10⁻⁶ kilograms, and is the standard unit for pharmaceutical dosing, vitamin labeling, food additives, and chemistry laboratory work. A typical aspirin tablet contains 325–500 mg of active ingredient, and recommended daily vitamin C intake is around 75–90 mg. The milligram is essential in toxicology (LD50 values are often given in mg per kg of body weight), water-quality testing (dissolved minerals in mg/L), and trace-element analysis. It relates to the gram (1,000 mg = 1 g), the microgram (1,000 µg = 1 mg), and the grain (1 grain ≈ 64.8 mg). Pharmaceutical prescriptions worldwide rely on milligrams, and accurate sub-milligram balances are standard in research and pharmacy environments.

• Prescription and over-the-counter drug dosing
• Vitamin and mineral supplement labelling
• Trace element analysis in laboratories

What is the Carat?

The carat equals exactly 200 milligrams (0.2 g) and is the universal unit for gemstone and diamond weight in the global jewelry industry. The word derives from the Greek 'keration' and the Arabic 'qīrāṭ,' both referring to carob seeds, which were once used as natural counterweights for weighing gems because they have remarkably uniform mass. The metric carat was standardized in 1907 at exactly 200 mg, replacing dozens of regional carat values that had varied between 188 and 213 mg. A 1-carat diamond is roughly 6.5 mm in diameter, and the famous Hope Diamond weighs 45.52 carats. The carat is distinct from the karat (with a 'k'), which measures gold purity (24-karat = 100% gold). It relates to the gram (5 ct = 1 g) and the milligram (200 mg = 1 ct). Gem dealers commonly use 'points' for fractions (100 points = 1 carat).

• Diamond and gemstone retail and valuation
• Jewellery manufacturing and design
• International gem certification (GIA, IGI)