How Do You Convert Carats to Grams?
Multiply carats by 0.2 to get grams, or divide by 5. The formula is: Grams = Carats x 0.2. The metric carat is defined as exactly 200 milligrams (0.2 grams).
Sam Okafor appraises jewelry for a client selling an estate. A ring contains a 3.5-carat emerald. Converting: 3.5 x 0.2 = 0.7 grams. Combined with the 4.2-gram 18K gold band, the total ring weight is 4.9 grams. He records both the carat weight and gram weight for the appraisal document.
Diamond Weight Reference
| Carats | Grams | Round Diamond Diameter |
|---|---|---|
| 0.25 ct | 0.05 g | ~4.1 mm |
| 0.5 ct | 0.1 g | ~5.2 mm |
| 0.75 ct | 0.15 g | ~5.8 mm |
| 1.0 ct | 0.2 g | ~6.5 mm |
| 1.5 ct | 0.3 g | ~7.4 mm |
| 2.0 ct | 0.4 g | ~8.1 mm |
| 3.0 ct | 0.6 g | ~9.3 mm |
| 5.0 ct | 1.0 g | ~11.0 mm |
Practical Applications
Engagement Ring Shopping
Dana Kowalski helps her sister compare engagement rings. One has a 1.2-carat center stone (0.24 grams) with 0.3 carats of side stones (0.06 grams). Total diamond weight is 1.5 carats = 0.3 grams. Another ring has a single 1.5-carat stone (0.3 grams). Both have the same total carat weight but look different because a single larger stone appears more impressive.
Insurance Valuation
Priya Patel updates insurance for her jewelry collection. Her necklace has a 8.5-carat sapphire = 1.7 grams and 2 carats of small diamonds = 0.4 grams. Total gemstone weight is 10.5 carats = 2.1 grams. The insurer requires both carat and gram weights on the itemized schedule. She photographs each piece on a scale for documentation.
Gemology Studies
Maya Singh learns gemstone identification in a geology elective. She weighs an unknown stone at 1.6 carats = 0.32 grams. Measuring its volume by water displacement at 0.09 mL, she calculates density as 3.56 g/cm3, consistent with topaz. Her professor confirms that density combined with carat weight helps distinguish gems from imitations.