Carat measures a diamond's weight, not its apparent size. It's the most widely known criterion among the public, and yet often misunderstood.
One carat equals 0.2 grams, or 100 points: a 0.75-carat diamond is therefore also described as "75 points". The word comes from the carob tree, whose seeds, remarkably uniform in weight, were once used to weigh precious stones.
A 2-carat diamond doesn't look twice as large as a 1-carat one: its diameter only increases by about 25 to 30%. It's the volume, not the diameter, that doubles. A good cut can also make a stone look larger than its actual weight suggests.
| Weight | 0,25 ct | 0,50 ct | 0,75 ct | 1,00 ct | 1,50 ct | 2,00 ct | 3,00 ct |
|---|---|---|---|---|---|---|---|
| Approx. diameter | 4,1 mm | 5,2 mm | 5,9 mm | 6,5 mm | 7,4 mm | 8,2 mm | 9,4 mm |
Price per carat jumps sharply at certain symbolic thresholds: 0.50 ct, 1.00 ct, 1.50 ct, 2.00 ct. A 0.96 ct diamond will often be noticeably cheaper than a 1.02 ct one, for a weight difference that's virtually invisible to the eye. Buying just under these thresholds is one of the simplest ways to optimise your budget without sacrificing appearance.
On a halo or pave ring, the figure quoted is sometimes the total carat weight (TCW), which adds up the centre stone and every small stone around it, not the weight of the main diamond alone. A "1 carat total" ring can therefore have a centre stone of only 0.70 carat, made up with accent stones. I always state both figures separately, so you know exactly what you're buying.
View the D Collection →For a round brilliant, 1 carat corresponds to a diameter of about 6.5mm. Apparent size then varies by shape and cut quality.
Because rough diamonds over one carat are far rarer to find in nature than fractional weights, and because price per carat jumps sharply right after each symbolic threshold.
It's the sum of the weight of every stone on a ring, centre stone and accent stones included. It shouldn't be confused with the weight of the main diamond alone.
Without a certificate, it's only an approximate estimate based on measurements. A GIA or HRD certificate remains the only reliable way to know the exact weight to the hundredth of a carat.
One carat weighs 0.2 grams, or 200 milligrams. It is divided into 100 points: a 0.50-carat diamond therefore weighs 0.1 gram.
The carat is a weight, not a size. The visible size, the diameter in millimetres, depends on the weight but also on the shape and proportions. The diamond size chart gives the equivalents.
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