Diamond Carat
Convert diamond carat weight to grams, milligrams, and troy ounces. Estimate diamond value by price per carat with interactive charts and detailed breakdowns.
About This Calculator
The Diamond Carat Calculator converts diamond weight between carats, grams, milligrams, and troy ounces while optionally estimating market value based on price per carat. Whether you are buying, selling, or appraising diamonds, this tool provides instant conversions and value estimates that help you make informed decisions in the diamond market.
The carat is the standard unit of weight for diamonds and gemstones worldwide. One carat equals exactly 0.2 grams (200 milligrams), a system standardized at the 1907 General Conference on Weights and Measures. The term carat derives from the carob seed, which was historically used as a reference for weighing precious stones due to its relatively uniform weight.
Diamond pricing follows a non-linear curve — larger diamonds are exponentially rarer and more expensive per carat. This calculator lets you enter a price per carat to estimate total value, but note that actual diamond prices depend on the 4 Cs: carat weight, cut quality, color grade, and clarity grade. Use the price estimate as a rough guide and always consult a certified gemologist for precise valuations.
Regional Notes
India: India is the world's largest diamond cutting and polishing hub, handling approximately 90% of global rough diamond processing. Diamond prices in India are quoted in INR per carat. Common sizes in Indian jewelry range from 0.10 ct (melee diamonds in temple jewelry) to 2+ ct (solitaire engagement rings). The Indian diamond industry follows the same metric carat system. GST applies at 3% on rough diamonds and 1.5% on cut and polished diamonds under the current regime.
US: The US is the largest diamond market globally. Retail prices are quoted in USD per carat. The Federal Trade Commission (FTC) requires accurate carat weight disclosure. A typical 1 carat round brilliant engagement ring diamond costs between $4,000 and $16,000 depending on cut, color, and clarity. The price per carat increases sharply above the 1 ct and 2 ct thresholds.
UK: UK jewelers quote prices in GBP per carat. Since Brexit, diamond import duties and VAT (20%) apply. The UK market follows Rapaport pricing for wholesale diamonds. Popular sizes include 0.30 ct (3 carat total weight for cluster rings) to 1 ct solitaires. The National Association of Goldsmiths provides consumer guidance on diamond grading and carat weight verification.
How Diamond Carat Weight Works
The conversion factors used in this calculator are: 1 carat = 0.2 grams = 200 milligrams = 0.00705479 troy ounces. These are fixed international standards that do not vary by market or region. The price estimation uses a simple linear formula — carat weight multiplied by price per carat — but real-world diamond pricing follows a step function with premiums at key weight thresholds.
Frequently Asked Questions
How many grams are in a carat?
One carat equals exactly 0.2 grams (200 milligrams). This standard was established by the metric carat system in 1907 and is universally accepted across all international gemstone markets.
How do I calculate diamond price from carat weight?
Multiply the carat weight by the price per carat. For example, a 1.5 carat diamond at ₹500,000 per carat is valued at ₹750,000. Note that diamond prices increase exponentially with carat weight due to rarity — a 2 carat diamond costs more than double a 1 carat diamond of similar quality.
What is the difference between carat weight and millimeter size?
Carat measures weight, not physical dimensions. Two diamonds of the same carat weight can appear different sizes depending on their cut, shape, and depth. A well-cut 1 carat round diamond typically measures about 6.5 mm in diameter, while a princess cut of the same weight may appear smaller face-up.
How many milligrams is a carat?
One carat equals 200 milligrams. For smaller diamonds, weight is often expressed in points — 1 point equals 0.01 carats or 2 milligrams. A 50-point diamond is 0.50 carats, and a 10-point diamond is 0.10 carats.
Is this diamond carat calculator free to use?
Yes, the Diamond Carat Calculator is completely free to use with no registration or hidden charges. You can convert carats to grams, milligrams, and troy ounces, estimate value based on price per carat, and share results via URL.
What is a troy ounce and how does it relate to diamonds?
A troy ounce (31.1035 grams) is the traditional unit for weighing precious metals and gemstones. One carat equals approximately 0.00705 troy ounces. While diamonds are always sold in carats for consumer transactions, the wholesale market sometimes uses troy ounces for bulk diamond parcels.
How do diamond prices vary by carat weight range?
Diamond prices jump significantly at key carat thresholds (0.5 ct, 1 ct, 2 ct, 3 ct) due to rarity and demand. A 0.90 carat diamond may cost 30-40% less than a 1 carat diamond of identical quality. Use the price per carat feature to estimate values across different weight ranges.
Can I share my diamond carat calculation results?
Yes, the calculator saves your carat weight and price per carat in the URL so you can bookmark or share the exact calculation with jewelers, appraisers, or insurance professionals by copying the page URL.