C1 Carat Weight

What is Carat Weight?

Carat weight is the standard unit of measurement for diamond weight. One carat equals 200 milligrams (0.2 grams). The term "carat" derives from the carob seeds historically used to balance scales when weighing gemstones, as these seeds were believed to have a remarkably consistent weight.

In the BGI 6C system, Carat is the first and most fundamental measurement. While it directly influences a diamond's price, two diamonds of identical carat weight can have vastly different values depending on their Color, Clarity, Cut, and Clara grades.

The BGI Carat Grading Standard

BGI employs high-precision electronic microbalances calibrated to measure weight to 0.001 carat (one-thousandth of a carat). Each diamond is measured in a climate-controlled environment to eliminate temperature and humidity variances that could affect readings. Our equipment is certified and recalibrated daily against international mass standards.

BGI certificates report carat weight to two decimal places (e.g., 1.50ct), with internal records maintained to three decimal places for traceability. This precision ensures that every BGI-graded diamond meets the highest standards of accuracy and consistency.

Carat Weight and Diamond Value

Diamond prices increase exponentially with carat weight, not linearly. A 2-carat diamond is typically more than double the price of a 1-carat diamond of similar quality, due to the rarity of larger rough crystals. This phenomenon is known as the "rare weight premium" and applies particularly at key thresholds (0.50ct, 1.00ct, 2.00ct, 3.00ct, 5.00ct).

Understanding the relationship between carat weight and visual size is also important. Different diamond shapes face up differently for the same weight. For example, a well-cut round brilliant of 1.00ct may appear larger than a poorly-cut 1.20ct diamond. BGI's 6C system considers these factors holistically.