Besides the remarkable sparkle of a diamond, one of the very first things you notice about an engagement ring is the size of the diamond. When it comes the 4Cs of a diamond, the carat size remains one of the most talked about characteristics of a diamond. In many cases, a future bride will frequently be asked what the size of her extraordinary diamond is.
For a diamond expert, it can come as second nature to establish a diamond’s size. But for everyone else, here’s an easy guide to help you establish and understand the meaning of a carat size.
Carat Size
Did you know that a carat (ct) usually refers to the diamond’s weight and not the initial size? One carat is equal to 200 milligrams. Carat is the unit of weight in which a diamond is measured; the term originated from the carob seed, which was historically used as a reference for weighing precious stones because of its consistent mass.
One carat weighs approximately 200 milligrams or 0.2 grams. In most cases, a diamond can have the same weight, but cost entirely different due to the other characteristics of the 4Cs.
As the carat weight of a diamond increases the price of the diamond will increase as well. The reason? The larger the diamond becomes the more exceptionally rare it is to find. Less than one in a million rough diamonds are able to be cut and polished into a faceted 1-carat diamond.
It’s important to note that even though the price increases with the carat weight, the size of the diamond will not necessarily be larger. When the carat weight of the diamond triples, the perceived size will triple along with it, however, the crown area will slightly double and the diameters of the diamond will go up with 45%.
Read More: The Term ‘Carat’ Explained
Comparing Different Carat Sizes
Carat Weight vs. Visual Size
Two diamonds with the same carat weight can appear different in size depending on their cut and shape. For example, a 1-carat marquise cut diamond will look larger than a 1-carat round cut diamond because elongated shapes (like marquise, oval, and pear) maximize the surface area visible from above.
The cut grade of a diamond also affects its perceived size. A higher cut grade allows more light to reflect, making the diamond appear larger, while a lower cut grade with poor light reflection can make even a larger carat diamond look smaller.
Fun Fact: The visible perception of elongated diamond cuts appearing ‘bigger’, like the marquise and oval shape, is what makes them a popular diamond cut for solitaire engagement rings.
Deciding on the Carat Weight and the 4 Cs
When it comes to making a decision on a certain carat weight first establish who you’re buying the diamond for; start with the size of the diamond since it’s the most visual part of a ring. Take a time trying out different diamond rings and determine which carat size suits you or the wearer’s hand better. The best way to start is trying on a quarter carat first and moving a size up as you try on different size engagement rings.
Remember that diamonds with a longer cut such as the pear-shaped or marquise diamond appear larger than a round diamond of the same carat weight. This is important to know if size and carat weight is of great importance. Once you’ve established the perfect size you can fit the colour and clarity according to your unique budget.
The following table gives a general guide for round brilliant diamonds, showing typical diameters for popular carat weights:
| Carat Weight | Approximate Diameter (mm) |
|---|---|
| 0.25 ct | 4.0 mm |
| 0.50 ct | 5.2 mm |
| 0.75 ct | 5.8 mm |
| 1.00 ct | 6.5 mm |
| 1.50 ct | 7.2 mm |
| 2.00 ct | 8.0 mm |
| 3.00 ct | 9.2 mm |
Note: These are average dimensions for round diamonds; other shapes may have different dimensions for the same carat weight.
Calculate a Diamonds’s Carat Weight
The best way to estimate the carat weight of a diamond is simply by weighing the rough stone in grams. Take the amount from the scale and divide it by 0.2 to determine the carat weight of a diamond. For example, a diamond weighing 0.4 grams would be 0.4 grams divided by 0.2 equals 2 carats (0.4/0.2=2.0).
- Weigh the diamond in grams.
- Divide the weight by 0.2 to get the carat weight.
What is the Best Carat Weight for a Ring?
The most popular and desired diamond carat weight for an engagement ring is widely considered to the 1.00-carats. However, if you’re planning to propose it’s necessary to consider your fiancé’s specific style and personality before deciding on the size of the diamond. In the end, the carat weight, cut, colour and clarity all play an important role in the overall size of a magnificent diamond.
Factors Influencing Perceived Carat Size
A smaller carat weight diamond will appear larger with the assistance of a higher cut grade, while a larger diamond will appear smaller with a lower cut grade.
Shape
Elongated shapes (marquise, oval, pear) look larger than round or square shapes of the same carat.
Cut Grade
A well-cut diamond reflects more light and appears larger, while a poorly cut diamond can look smaller than its actual carat weight.
Setting Style
A delicate or slender setting can make a diamond look bigger, while a thicker setting may make it appear smaller.
Learn More About Diamonds and Diamond Carat Size
At the Cape Town Diamond Museum, visitors can explore the fascinating world of diamonds and learn about the history of the history of diamond mining in South Africa.
Featuring life-size replicas of some the world’s most famous diamonds, mining gear, historical artefacts, and specimens of natural kimberlite, the museum offers an intimate and educational experience for visitors at the V&A Waterfront. Here, guests can also witness the transformation of rough diamonds with live diamond-polishing and see how diamond jewellery is crafted from start to finish.
Book your diamond museum tour today.
