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.

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.

Convert carat weight and estimate diamond value

Carat Weight:

Price per Carat (₹):

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.

Regional Notes

India: India is the world"s largest diamond cutting and polishing hub. Diamond prices in India are quoted in INR per carat. Common sizes range from 0.10 ct melee diamonds to 2+ ct solitaires. GST applies at 3% on rough and 1.5% on polished diamonds.

US: The US is the largest diamond market globally. A typical 1 carat round brilliant diamond costs between $4,000 and $16,000. The FTC requires accurate carat weight disclosure. Prices increase sharply above the 1 ct and 2 ct thresholds.

UK: UK jewelers quote in GBP per carat. The UK market follows Rapaport pricing for wholesale diamonds. Popular sizes include 0.30 ct cluster rings to 1 ct solitaires. VAT at 20% applies on diamond purchases.

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. 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.

Is this diamond carat calculator free?

Yes, the Diamond Carat Calculator is completely free to use with no registration required.