Diamond Carat Weight
Most people think that a “carat” is a size or a physical dimension of some sort. That is completely incorrect and unfortunately leads to many misunderstandings.
A “carat” is simply a unit of mass or weight. It equals 200 mg or 1/5th of a gram, depending upon how you choose to describe it. Like a pound or an ounce, it is strictly a way of describing weight…not physical size, or dimensions, or surface area, just weight.
As stated above, diamonds, and other precious gemstones have been measured using the term “carat” for many centuries. Long ago, it was made a metric unit as the “Old World” carat turned out to be almost exactly 200 mg. It became an extremely convenient way to base a pricing system. It is most often abbreviated as ct. Being a metric unit, a carat is broken up into 100 “points”. So, a “fifty point” diamond weights .50 ct. or exactly one half carat.
Mother Nature decided that diamonds don’t occur in large sizes very often. Her decision, not ours, and we just need to deal with that fact. Diamonds are priced on a “per-carat” basis. You could equate it to buying fruit on a “per-pound” basis. For example: If you buy two pounds of apples at $2.00 per pound, you will spend $4.00. If you buy a 2.00 ct. diamond at $10,000.00 per carat, you will spend $20,000.00. Or, if you buy a .50 ct. diamond at $5,000.00 per carat, you will spend $2,500.00.
Pretty much everybody knows that diamonds get rarer as they get bigger. But, the rarity factor of diamonds, as they get larger, does not go up in an even, consistent manner! For example: A 1.00 ct. diamond isn’t twice as rare as a .50 ct. diamond, it’s a hundred times rarer! As a result, there are some significant price changes when one jumps from one weight category to another, even if all the other technical factors remain constant. An example of this would be a round diamond with a certain combination of cut quality, color grade, clarity grade and weighing .98 ct. It might sell for $10,000.00 per carat with a net price of $9,800.00. But another round diamond, with EXACTLY the same cut quality, color grade and clarity grade, but weighing 1.02 ct. might sell for $13,000.00 per carat. That works out to a net price of $13,260.00!!! For a diamond that only weighs .04 ct. more. That’s 4% heavier but about 30% more costly.
The actual difference in diameter of those two diamonds is measured in tenths or even hundredths of a millimeter!!! That is essentially an imperceptible amount to the naked eye, virtually impossible for the human eye to see. So which one is the best value?
In our culture, “size” or “carat weight” has become the all-important factor and more diamonds are purchased because of size than anything else. It is a personal taste factor again, but one that has enormous influence on the final price of the diamond purchased. It is tantamount to purchasing a house or a car by the pound! If asked how much your car or home weighed, without asking you anything else, you would probably really wonder what the person quizzing you was thinking…and/or drinking!