DIAMOND CARAT 

Diamond Carat is the most visual of the 4 C’s of diamonds. Carat is a weight measure for a diamond that is globally recognised. Not to be confused with karat (a measure of gold purity), a 1.00 carat or ct diamond weighs 0.20 grams. Contrary to popular belief, the carat is not the size of the diamond. The size of a diamond is measured in millimetres by length and width or in other words the diameter of the diamond. It typically takes about 250 tons of rock mining to produce just 1.00ct of diamond. That is why diamonds are rare and expensive.

Diamonds come in a variety of shapes and carat weights. A diamond cutter’s highest priority is to maximise carat weight of a diamond. The larger the diamond, the rarer and therefore more expensive it is. Diamonds are weighed with carat/gram scales very precisely to the 0.01ct. This measurement for diamond weight is universal and is used by countries around the world. Before the standardisation of the metric carat in 1907, there were a variety of terms and measurements for the diamond. In the past carob seeds were used to measure carat weight as it was believed that the mass of each seed did not vary much. However, this was not completely accurate. Over time carat weight became standardised and has now also become a point of reference in when looking at the certificate of any diamond regardless of which institution certifies the diamond.

DIAMOND SCALE: THE RANGE

Diamonds within each carat range have average millimetre sizes so you can approximate their visual size. Although each diamond is unique, these millimetre measurements are typically the norm, especially since diamonds today are cut with machines to ensure precision. To truly understand the diamond’s size, evaluate the measurements. Well cut round diamonds have less depth than well cut fancy shaped diamonds (diamonds other than Round). For example a 1.00ct round diamond will have ~6.40mm length/width vs a 1.00ct Princess diamond, which will have ~5.50mm. Fancy shapes tend to have more weight and less size. Thus round cut diamonds have a premium versus fancy shapes of the same carat weight. Visually, it is very difficult to discern the difference between diamonds that vary 5% - 10% in carat weight. For example, 0.95ct vs. 1.00ct. One additional factor that affects diamond size is the cut of the diamond. If a diamond is cut too deep, it may looks smaller than a lower carat diamond. When looking at carat weight and millimetre, it is also important to consider length to width ratios for each diamond shape. These will help you understand if a diamond is too shallow or too deep or if it has the correct and desired proportions for your shape. A deep 1.00ct diamond can possibly look visually smaller than a 0.95ct shallow cut diamond. View our comprehensive diamond size and millimetre chart.

CARAT PRICE EFFECT

Diamond pricing increases exponentially, not linearly, as diamond carat weight increases. Once a diamond hits its critical weight, the price bumps up. The critical weights are: 0.30ct, 0.40ct, 0.50ct, 0.70ct, 0.90ct 1.00ct, 1.50ct, 2.00ct, 3.00ct, 4.00ct, 5.00ct, 10.00ct. Diamond cutters will do everything they can to keep the diamond weight at or above each critical weight. Therefore, while it is often recommended to purchase 0.95ct diamonds vs. 1.00ct diamonds, it’s very difficult to find 0.95ct diamonds. Additionally, diamond manufacturers and suppliers know this “trick” and so they’ll price their diamonds accordingly.

The average diamond carat weight is 0.90ct. Consumers prefer Carat above the other C’s of diamonds because carat is the most visual C. When pricing diamonds, think about carat on one side and the other 3 C’s on the other side. In order to fit your diamond budget, as you increase carat, you may need to reduce the other C’s. Vice versa, if you increase the other C’s, you may need to decrease carat. Visually, a larger carat size will fill up more of the hand. However, if you do not maximising for cut and clarity, the reflection of light within the diamond will be hindered. This means that although you may get carat size, you will not get the sparkle from the diamond. Therefore, it is important to have a balance of all the 4 C's even if you are optimising for carat weight for your engagement ring diamond.