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Diamond Weight Categories

Diamond Carat Weight

Diamonds are the heaviest and densest material known to man. Diamonds are weighed in carats. A carat is .2 grams. A gram of diamond would be a massive 5 carats. Very large in diamond terms although the actual diamond is small.

A carat is further divided into Points, and there are 100 Points to a carat. So 1 point is .002 of a gram. Very small indeed.

There is a scale of weight for Diamonds and this is shown here:

Weight Size (diameter) Weight: pts (diameter) Weight: fractions
0.10ct 3.00mm 10pts 1/10th
0.20ct 3.85mm 20pts 1/5th
0.05ct 1.00mm 5pts 1/20th
0.25ct 4.10mm 25pts 1/4th
0.33ct 4.55mm 33pts 1/3th
0.40ct 4.80mm 40pts 4/10ths
0.50ct 45.15mm 50pts 1/2th
0.66ct 5.72mm 66pts 2/3th
0.75ct 6.00mm 75pts 23/4th
0.90ct 6.40mm 90pts 9/10ths
1.00ct 6.65mm 100pts 1 carat
1.50ct 7.50mm 150pts 1&1/2 carats
2.00ct 8.10mm 200pts 2 carats

Due to the minute differences in the weight of most diamonds they should always be accurately weighed on an electronic scale to the nearest 1000th of a carat (.001). Stones are always rounded up or down to the nearest 1000th of a carat by the way.

The other factor to consider with weight is a certificate. Where a diamond has been assessed and weighed at a laboratory, a certificate should be issued to confirm the assessment. No stones should ever be purchased without a certificate from a bona fide laboratory.

Code     Laboratory
ADL Antwerp Diamond Laboratory
AGAAmerican Gem Apraisal Laboratories
CSAJewellery Council of South Africa
DGLDiamond Grading Laboratories (London)
EGIEuropean Gemmological Institute (Antwerp)
EGLEuropean Gemmological Institute (Antwerp & London)
PNFP N Ferstenberg Pbv A
GAGGesellschaft fur Angewandte Gemmologie
GANGemological Institute of Antwerp
GIAGemological Institute of America
GIINational Gemological Institue of Israel
GILGem Information Laboratory
GTLGem Testing Laboratory of Great Britain
NGLNorthern Gemmological Laboratories (UK)
HRDDiamond High Council (Antwerp)
HRGHeinz R Gartner, DGemG, FGA (Germany)
IGIInternational Gemmological Institute (Antwerp)
PSLPrecious Stone Laboratory (London)
VPTVerena Pagel-Theisen, DGemG FGA (Germany)
WGWerner Galia, DGem, (Germany)

It cannot be iterated enough to ensure that all diamonds you buy should have a certificate from one of the above laboratories.

See also Diamond Appraisal

More information on carat weight can be obtained here Weight of Diamonds


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