Do you want to become a diamond expert, so you can impress your significant other when you pop the question? If you’re nodding, here’s a good place to start: Are diamond weight and diamond size the same? You’ll sometimes see these terms used interchangeably, but they’re actually completely different! We’re here to help you expand your knowledge, so read on to learn more.

What is Diamond Weight?

Diamond weight is exactly what you’re probably thinking. It describes how heavy or light a gem can be, and it’s measured in carats. You can identify carats by the letters “ct,” which are written after a diamond’s weight. One carat is equivalent to 0.20 grams (or 200 milligrams), but carats are often represented as points, where one represents 100 points. Ex. One carat would be 1.00 ct and a half carat would be 0.50 ct.

*Pro Tip: For couples ready to say “I do,” one carat is the diamond weight of choice, making it a “magic size.” That means 1.00 ct diamonds tend to be more expensive simply because they’re popular. So, keep an eye out for slightly cheaper stones with similar weights (aka “off-size diamonds”). For example, a 0.95 ct diamond will look just as stunning as a 1.00 ct gem. Only jewelry experts will be able to tell the difference!

What is Diamond Size?

Diamond size, on the other hand, indicates how large or small a stone appears. Typically, the diameter is measured and represented in millimeters. But for fancy cut stones, like pear and marquise shapes, two measurements are sometimes provided, representing the length and width. Or, you might just see one dimension for length.

Here are some standard sizes that you’ll likely find for 1.00 ct diamonds. However, sizes might vary somewhat, depending on how each stone is cut.

❖Round cut diamond: 6.5 mm

❖Princess cut diamond: 5.5 mm

❖Asscher cut diamond: 5.5 mm

❖Cushion cut diamond: 5.9 mm

❖Oval cut diamond: 7.7 mm x 5.7 mm

❖Pear cut diamond: 7.7 mm x 5.7 mm

❖Marquise cut diamond: 10 mm x 5 mm

*Pro Tip: How do these measurements correlate to your partner’s finger? Find a ruler, count the millimeters and compare with their finger. Or, if you want to keep the proposal a surprise, measure against your own finger. And if you really want to get creative, you can even cut a piece of paper with the corresponding dimensions. That way, you can visualize how the diamond shape and size will look on their finger.

Which is More Important: Diamond Weight or Diamond Size?

The simple answer is neither! Both are equally important. As carat weight increases, so does the price of a diamond. That means bigger gems are rare and valuable. A large sparkler is great for making an impression, but you’ll ultimately want to select a diamond that works with your budget.

You’ll also want to pay attention to the diamond’s size. While it may be tempting to opt for a massive-looking stone, it might not be a flattering choice. (In case you didn’t know, certain diamond shapes can make fingers look longer and slimmer!) Large gems might also be cut too shallowly. This often results in a duller appearance, as light escapes through the bottom portion of the diamond.

*Pro Tip: You should really focus on all diamond characteristics — cut, color, clarity and carat weight (aka the 4 C’s) — when considering an engagement ring. They essentially work together to create a stone’s overall look!

Have a question? We can help!

Gage Diamonds is Chicago's premier jewelry showroom and online retailer of engagement rings, wedding bands, and fine jewelry. We offer a selection of dazzling handpicked diamonds, including certified natural and lab grown diamonds.

We’re committed to helping you find the ring of your dreams. For inspiration, browse our selection of natural and lab grown diamonds, or set up an appointment with a member of our trusted staff at our in-person showroom.

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