Diamond carat weight is probably the easiest of the 4Cs to understand when we are talking about diamonds. Basically, you put the loose (unmounted) diamond on a scale and write down the carat weight reading… simple!
In general, you can trust the diamond carat information provided on a certificate. This is because every country in the world has tough rules about misrepresenting diamond carat weight.
When you are out shopping, you should pay close attention to details and make sure that the carat weight of the diamond you are buying is expressed to the one hundredth of a carat. This means you should see carat weight being represented by 2 decimal points like 1.27ct. or 0.83ct.
5 Things You Need to Take Note Of
#1 – You shouldn’t confuse diamond carat weight with the physical size of a diamond because these 2 are totally different things. Two round brilliant cut diamonds that have the exact same diamond carat weight (they weigh the same when placed on the diamond scale) could be very different in measurement of their diameters. That is to say, one diamond could actually look and be physically smaller.
This has to do with how the diamond cutter has distributed the weight throughout the diamond. If you want more details about this, you can refer to the diamond cut section where I explain how a cutter can keep additional carat weight from the original diamond rough.
#2 – When it comes to diamond buying, there are some diamond carat weight ranges that can command higher prices for a diamond just because it close enough to a certain “magic” weight.
For example, a diamond that weighs 0.90ct. can see a jump in prices because it is close enough in weight to be considered a one carat diamond. Although it does not weigh out at one carat yet, some jewelers consider it to be a “light 1 carat” diamond.
To give you a better idea of the trade terms used, you can refer to the carat weight groups below:
(0.23-0.29ct.) – 1/4 ct.
(0.30-0.37ct.) – 1/3 ct.
(0.38-0.45ct.) – 3/8 ct.
(0.46-0.49ct.) – Light 1/2 ct.
(0.50-0.69ct.) – 1/2 ct.
(0.70-0.89ct.) – 3/4 ct.
(0.90-0.99ct.) – Light 1.00 ct.
(1.00-1.49ct.) – 1.00 ct.+ (along with a jump at 1.25ct.)
(1.50-1.99ct.) – 1.50 ct.+ (along with a jump at 1.75ct.)
#3 – If you don’t know what a 0.45ct., a 0.75ct., or a 1.10ct. diamond looks like, go to a local jewelry store, they would be happy to show you for free. Otherwise, you can refer to couple of charts that will help when visualize physical size here.
You could also ask a family member or coworker about the size of the diamond they are wearing.
#4 – All of the diamond carat weight in a piece of diamond jewelry can be added up and labelled as a term called “total carat weight”. For example, a “3 stone ring” could have a 0.34ct., a 0.37ct., and a 0.55ct. diamonds in it and the total carat weight of the ring would be1.26ctw.
Do note that the jeweler should provide you with some indication that it is a total carat weight.
#5 – Loose diamonds can be put on a scale to determine the actual carat weight. However, once a diamond has been mounted into a piece of diamond jewelry, that opportunity is no longer available.
In order to find the diamond carat weight of mounted diamonds, you can visit an appraiser and ask him to estimate it based on its physical measurements. Do note that it’s not very accurate (±10-15%) but you can’t be taking diamonds out of their mountings in order to weigh them because jewelers won’t do that for you.
This is why it’s always best to know the diamond carat weight, diamond clarity, and diamond color before any diamonds are set into a mounting. A neutral 3rd party certificate would provide these information readily and save you the hassle of doing it by yourself.