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Carat is a measurement unit of the weight of both diamonds and other gemstones. One carat is equal to 0.2 gram which is about the weight of a paperclip. Carat weight is not related to how nicely a diamond sparkles. In fact, two diamonds of equal weight can have very different values and brightness depending on the other members of the 4C’s. In fine jewelry, including those at AGY, diamonds typically weigh two carats or less, but their value depends on achieving that sparkle through other qualities such as cut, color and clarity.
Among the 4C’s, carat is the one that has the biggest impact on the price. It’s a universally recognized measurement system that assesses the diamond’s value and determines its price and appearance. The higher the carat weight, the bigger the diamond. And bigger diamonds tend to be more noticeable and flashier, which is why they are more desirable and expensive. However, it's just one piece of the puzzle when it comes to picking out the perfect diamond. The balance of the 4C’s is the best way to make a smart and informed purchase.
Carat might sound like it tells you how big a diamond is, but it is actually about a diamond’s weight, not its physical size. However, a bigger diamond will usually weigh more carats. But a bigger diamond does not always mean a better diamond. Two diamonds with the same carat weight can look very different because of variations in density and cut. That’s why it's important to consider both carat weight and cut when choosing a diamond, so you don't end up paying extra for weight that won't even be visible.
Our carat chart provides a helpful visualization of how various diamond carat weights appear at their actual size, viewed from above, in different shapes. Keep in mind that other factors, like the diamond's proportions (length-to-width ratio) and its cutting style (table size and depth), can also influence its final look. So, your diamond might show some slight variations compared to the chart.
Carat weight isn't the only factor determining a diamond's perceived size. There are two other factors interfering: cut and shape.
Cut: A poorly cut diamond, even with a high carat weight, might look smaller due to a shallow cut or a thick girdle that hides some of the stone.
Shape: Elongated shapes like marquise, emerald, oval and pear can appear larger than their carat weight suggests because they spread out more. Conversely, round brilliant cuts might show a bit less surface area for their weight due to their more compact form.
As carat is not the only factor affecting the size, you can create the illusion of a larger diamond with simple tricks.
A one carat diamond will typically be around 6.5 millimeters in diameter. And the perceived size can vary depending on the cut.
The Cullinan Diamond holds the record for the largest gem-quality diamond ever found and it weighs 3106 carats. It was later cut into several polished stones, with the largest one weighing 530 carats.
There are two main methods jewelers use to measure a diamond's carat weight. The first and most precise one is with a specialized diamond scale. These incredibly precise scales are calibrated to measure in carats and points (hundredths of a carat). For already cut diamonds, jewelers can sometimes estimate the carat weight based on the diamond's diameter using a formula. However, this method is less precise.
A 1/3 carat diamond is bigger than a 1/4 carat diamond.
How a diamond's facets interact with light
The natural tint inherent in white diamonds
A measure of the purity and rarity of a stone