CARAT WEIGHT VS. GEM SIZE
Gem weight is measured on the metric carat scale. According to the scale, one carat is equivalent to 200 milligrams (0.20 grams), divided into 100 points for precision. For example, a sapphire weighing half a carat may be referred to as 0.50 carats or “5 points”. Thus, carat weight not only applies to diamonds but colored stones, too.
There is a common misconception that carat weight represents visual size. However, they are not actually the same thing and should not be confused for two reasons, namely:
1. Two gemstones of the same proportions (i.e., shape and carat weight) may appear different due to their cuts. For example, gems with deeper cuts are likely to appear smaller than ones with shallower cuts.
2. Gems have different densities (mass per unit volume). Sapphires, for example, are denser than diamonds, meaning a one-carat sapphire will appear smaller than a one-carat diamond.
The best way to visualize the size of a gemstone is by its dimensions, the top diameter in particular.
GEMSTONE CARAT WEIGHT CHART
Be aware that the carat weights and gem sizes in the following chart apply to diamonds cut to ideal proportions and that colored gems will have different weights to the ones listed below. This is because gem cutters will usually cut colored gems with a greater volume than diamonds when working on standard gem sizes.
SHOULD YOU BUY A GEM BASED ON CARAT WEIGHT OR SIZE?
When buying gems, it’s important to consider what you need them for, as this will determine whether you need to buy based on size or weight. For instance, if you’re buying a stone for an existing jewelry setting, then it’s best to buy by size and not by estimating weights. On the other hand, if you are buying a stone for a custom-made setting, then you are free to buy the stone that appeals most to you.
While it’s good to observe weight and size when buying diamonds and other stones, you shouldn’t limit yourself to these characteristics alone – also consider the gems as a whole and the way they appear to the naked eye.
Frequently Asked Questions
However, there is no “ideal” carat weight or size for engagement ring stones, and the one you choose will ultimately depend on your personal preference and budget. Also, remember that carat weight influences price more than the color, cut, or clarity of the gem. So, if you’re looking to save money without compromising on appearance, opt for a lower carat weight.
Diameter or length is measured in millimeters (mm) across the top of the gemstone as it is viewed from above.
Carat weight is measured in carats (ct), where one carat (1.00 ct) is equal to 200 milligrams or 1/5th of a gram. When looking at gemstones, it is important to remember that gem sizes do not necessarily reflect their weight and vice versa. Traditionally, gems are priced per carat.
Gemstone density (also called specific gravity) describes a gemstone’s weight relative to how it behaves in a liquid (i.e., how much it weighs in water). Different gem varieties have different densities, which can also influence their carat weight. For example, sapphire and ruby have a specific gravity of 4.0, while other gems like amethyst and emerald are lighter. Diamond has a specific gravity of 3.52, which means a one-carat diamond will not be the same size as a one-carat sapphire or emerald.
Thus, to get two varieties of gemstones that look the same, you need to disregard the gems’ carat weights and measure them according to their size in mm.