Diamond Carat weight size scale

Carat is the standard unit of weight measurement for gemstones.
One carat is equivalent to 0.20 grams.
One gram is equivalent to 5 carats.
One pound is equivalent to 2268.2 carats.
Carats are divided into 100 points, like cents to a dollar.
A ½ carat diamond can also be described as a fifty- pointer.

What is the difference between carat & karat?
In the US and Canada, Carat (abbreviated ct.) refers to the standard unit of weight used for all gemstones. Karat (abbreviated kt.) refers to the purity of gold. 24-karat gold is 99.9% gold, 18-karat gold is 75% pure gold and 14-karat is 58.5% pure gold.

Diamond Carat Weight Size Lesedi la Rona


Do carat weight and size mean the same thing?
Not exactly, although the terms are commonly used interchangeably. Carat is a unit of weight (mass) and size refers to dimensions measured in millimeters (mm). The size of a 1-carat round brilliant diamond can range from approximately 6.20 mm to 6.80 mm in diameter, depending on the depth. A deep cut is smaller in diameter and a shallow cut is wider in diameter. A shallow cut makes a diamond look bigger (described as 'spread') but diamonds that are either too shallow or too deep sacrifice 'Cut' quality and therefore a diamond's brilliance.

Why are diamonds weighed in carats?
The word carat is derived from the carob bean, known for its uniform weight, which was historically used to balance scales when weighing gemstones. In 1907, the Fourth General Conference on Weights and Measures accepted the metric carat (200 mg) as a standardized unit of weight.

Diamond Size Carat Weight

How are diamonds weighed?
Exact measurement of carat weight is important because a slight difference in carat weight can have a large impact on price. GCAL weighs diamonds on precise electronic balances that are calibrated and verified daily according to ISO requirements. Carat weight is measured to a thousandth of a carat and then is rounded to a hundredth of a carat. If the thousandth of a carat is 9 then the weight is rounded up, otherwise, the weight is rounded down. For example: If a diamond weighs 1.148 carats, GCAL rounds down to 1.14 carats. If a diamond weighs 1.149 carats, it is rounded up to 1.15 carats.

How can I calculate the carat weight of my diamond if it's mounted in jewelry?
Mounted diamonds can be precisely measured using digital millimeter gauges. Once the Length, Width and Depth measurements have been determined, formulas for each common diamond shape can be used to calculate the approximate carat weight.

What is the largest diamond ever found?
The Cullinan diamond, discovered in 1905 in South Africa, weighed 3106.75 carats in its rough form. The largest faceted diamond cut from the Cullinan weighed 530.20 carats.

Size Diameter Carat Weight Round Diamonds
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Each panel of a GCAL Certificate tells a story to the customer.
  • Panel 1

    Verifies the identification process

  • Panel 2

    Verifies the 4C's quality grading

  • Panel 3

    Illustrates the quality of cutting and proportions revealing the skill of the diamond cutter

  1. 1Gemprint
  2. 2Laser Inscription
  3. 34C's Grading
  4. 4Photomicrograph
  5. 5Hearts & Arrow
  6. 6Optical Brilliance
  7. 7Optical Symmetry
  8. 8Proportion Diagram