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  • Writer's pictureSimo R.

Diamond Buying 101 Part 3 - Carat

When looking to buy a diamond for any reason, be it for a present, special occasion or just to show someone your appreciation, you will be quickly immersed in the world of numbers and letters that indicate a diamond's value. To help decipher some of these things I'm going to explain how diamonds are valued in the industry and what you should be looking for.

Firstly, what you should be looking for is what you can afford. Diamonds are amazing creations of nature and will always be held in high regard but you should never go overboard just to get 1 grade higher or something because the salesperson is pushing it on you. From my experience in the jewellery industry basically any salesperson will either be on commission or some kind of bonus system that will provide them a benefit for trying to upsell you. Resist their pressure and buy exactly what you know you can afford. A good jeweller will always be able to work with essentially any budget to find or create a beautiful piece of jewellery for any occasion.

When looking for a piece of diamond jewellery you may have heard of the 4Cs which are Cut, Clarity, Carat and Colour. The 4Cs have been around for many years and have become the standard on how we grade and buy diamonds and depending on the region of the world or who you are buying the diamond from there are a variety of systems to use when grading by these criteria. Nowadays however, I believe there should be 5Cs though with the emergence of origin tracking and lab created diamonds. The last C should be Creation (AKA origin).



The carat of a stone is one of the easiest for people to understand. Not to be confused with the word "karat", which refers to the fineness of gold in a piece of jewellery, the carat is a measurement of weight and is an industry wide used measurement. There used to be other measurements of weight, such as grains, that were used, however, they have mostly been discontinued. If they are still being used then it's usually for specific purposes, like describing weight in pearls.

The term carat is usually abbreviated to "ct" and described 1/5th of a gram as a unit of measurement which means that a 1.00 ct diamond weighs 0.2 g or 200 mg. Carats should be measured accurately to two decimals. These decimal numbers are sometimes referred to as "points". One "point" is equal to one hundredth of a carat (0.01 ct) so a 10-point diamond would weigh 0.10 ct.

Another term you may come across when dealing with the weight is carat total weight sometimes abbreviated to "cttw". This is just taking the total weight of all diamonds on the piece of jewellery and adding them up. A lot of the time when you're shopping, retailers will separate the center stone and then give you the total weight including the center stone. For example, you might look at a ring and be told the center stone is 0.50 ct and the ring has 1.25 cttw which means that all the accent or side diamonds will total 0.75 carats.

The above chart has some more common diamond sizes and shapes in mm and the corresponding approximate carat weight you would expect for that size. The PDF version below can be printed out for accurate measurements to give you an idea what size the stone will look like. There will always be a slight variation depending on how the stone is cut that will adjust the carat weights shown here but this gives a good rough idea of what size you would expect for the shape and size of the stones shown.

Size Chart
Download PDF • 214KB

One other thing to know about the diamond industry, there are specific price points if you were looking for a diamond to put into a custom ring. A diamond weighing around 0.90 ct will be much less than a 1.00 ct diamond and depending on how it's cut can look very similar to each other in physical size so it might be better to go with a slightly smaller or odd weight instead of going for the more common 0.25, 0.33, 0.50 or 0.75 carat diamonds. The best way to find a diamond like this is to talk to a reputable jeweller or diamond dealer. Explain what your budget is and they should be able to find a stone that will be the best value for a similar size look.

One option if you are trying to get a lot of sparkle and shine, but at a lower budget, is to look for stones that are many small diamonds or set in specific mounts, like illusion settings, that mimic larger diamonds or make the diamonds look bigger than they are. A ring with a lot of smaller diamonds with 1 cttw is much less expensive than a ring with a single 1 ct diamond.

When you're shopping for a diamond, make sure that you keep your budget in mind and don't overspend on a bigger diamond when you can get almost the same look for less if you have a knowledgeable diamond dealer or salesperson. Carat weight does affect the price of stones but it shouldn't be the main thing you're looking at. Usually, it's better to spend the money on a quality stone rather than a big one, but in the end, it's a personal choice that you'll have to make based your budget and style.


If you are interested in getting your diamond appraised or even just graded or verified then visit us at 1612 Lasalle Blvd in Sudbury, Ontario, right next to Red Lobster and across from the Part Source. You can also contact us by email at or by phone at (705) 222-1221.

To read more about the services available check out our available services here.

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