Carat is a unit of weight used to measure diamonds and other gemstones. While many assume it represents size, carat actually refers to weight—one carat equals 0.2 grams, roughly the weight of a paperclip. Understanding carat weight is crucial in determining the value of a diamond, but it is only one aspect of what makes a diamond beautiful.
The carat system dates back to ancient gem traders who used carob seeds as standard weights. However, the system varied internationally until 1913, when the modern metric carat was introduced. Today, a carat weighs the same worldwide, ensuring consistency in gemstone measurement. Carat weight can significantly impact a diamond’s price, but two diamonds of the same weight can appear very different depending on their cut and shape.
Carat measures weight, not visual size. A diamond’s perceived size depends on factors such as shape, cut, and depth. For example, a one-carat round diamond typically measures about 6.4mm in diameter, while a one-carat round sapphire appears slightly smaller at around 6.0mm due to differences in density.
Gemstones with an elongated shape, like ovals or emerald cuts, often appear larger than round diamonds of the same carat weight. Similarly, a diamond with an ideal cut can maximize its face-up appearance, while a poorly cut stone may hold excess weight in its depth, making it look smaller than its actual weight suggests. Choosing a well-cut diamond can help maximize its visual impact and ensure that it looks as impressive as possible for its weight.
One carat equals 200 milligrams and is divided into 100 ‘points’ for precise measurement. For example, a 0.75-carat diamond is sometimes referred to as a “75-point” diamond. Experts use highly sensitive micro-balance scales to measure carat weight accurately, ensuring consistency across the industry.
While carat weight is an essential metric, it should be considered alongside other factors like cut, colour, and clarity. A diamond with a slightly lower carat weight but superior cut can appear larger and more brilliant than a heavier diamond with a poorer cut.
No, carat weight does not directly determine a diamond’s visual size. Two diamonds of the same carat weight can look very different based on how they are cut.
For example, a round diamond with a deep cut may appear smaller than one with a well-proportioned cut because more weight is hidden below the surface. Likewise, elongated shapes, such as pear or marquise, tend to appear larger than round diamonds of the same weight. A well-proportioned diamond is designed to maximize its size and brilliance while maintaining structural integrity.
CTW (Carat Total Weight) refers to the combined carat weight of all diamonds in a piece of jewellery. For example, diamond stud earrings with a 1ctw mean each earring contains a 0.50-carat diamond. It’s important to clarify whether a listed weight refers to a single stone or the total across multiple stones in a jewellery piece.
This is particularly important when considering pieces like eternity bands or multi-stone rings, where the weight is distributed across several diamonds. The appearance and value of the piece depend not only on the total carat weight but also on the individual sizes and arrangement of the diamonds.
Traditionally, a 1-carat diamond has been the standard size for an engagement ring. However, the final choice ultimately depends on budget and personal preference. Lab-grown diamonds have made larger carat weights more accessible, allowing customers to purchase bigger engagement ring diamonds within a broader range of budgets.
Lab-grown diamond engagement rings tend to be slightly larger than their natural counterparts, mainly due to their affordability and wider accessibility. It’s becoming increasingly common to see couples choosing 2ct+ diamonds for engagement rings, reflecting a growing trend toward bold, statement pieces. A well-cut, high-quality diamond will always stand out, regardless of its carat weight.
Carat weight is one of the 4Cs (cut, colour, clarity, and carat) used to assess diamonds. While carat significantly impacts a diamond’s value, larger diamonds are rarer, making them more expensive. However, carat weight alone doesn’t determine a diamond’s beauty—cut, clarity, and colour all play crucial roles in its overall appearance.
We generally recommend choosing a slightly smaller carat weight with excellent cut, clarity, and colour, rather than sacrificing these qualities for a larger but lower-quality stone. With expert guidance, you can find a diamond that fits your needs while maximizing its brilliance and impact.
Carat weight heavily influences diamond pricing, but it’s not a simple linear increase. Larger diamonds are significantly rarer, so prices rise exponentially rather than proportionally.
The industry also recognizes ‘magic sizes’—common weight benchmarks like 0.50, 0.75, and 1.00 carats—where prices jump considerably. For example, a 0.97-carat diamond and a 1.03-carat diamond of the same grading may look nearly identical, but the latter will cost more simply because it surpasses the one-carat threshold. Choosing a diamond slightly below one of these magic sizes can offer better value without a noticeable difference in appearance.
No, several factors contribute to how large a diamond appears:
We are highly selective about the diamonds & coloured gemstones we offer in our Gem Vault. Every stone is carefully selected by our founder—a certified gemmologist with the International Gem Society (IGS) and an accredited diamond grader with the Gemmological Association of Australia (GAA). Each and every stone is assessed with precision and care, upholding our strict standards of quality, traceability, and ethical sourcing. Explore the Gem Vault to discover our curated collection of loose diamonds and coloured gemstones, or contact us to source something specific for your design.
