Crack the Code: Mastering Diamond Carat and Size

engagement ring. Since you’ll often encounter it while shopping for your engagement ring, here are key insights, including carat weight and pricing. For a quick grasp of Diamond Carat, watch our co-founder Anubh discuss this topic below.

How much does a diamond carat weigh?

A diamond weighing 1 carat (or ct) is equivalent to 0.20 grams. Contrary to common belief, carat refers to weight, not size, which is measured in millimeters (length by width), meaning the diamond’s diameter. Producing a single 1 carat diamond typically requires mining approximately 250 tons of rock, explaining why diamonds are rare and expensive.

Diamonds vary in shapes and carat weights, and diamond cutters prioritize maximizing carat weight. Larger diamonds are rarer and thus more expensive, weighed precisely to the nearest 0.01ct.

Before carat became a universally adopted standard in 1907, various measurements existed for diamonds. At one point, carob seeds were used, based on the false belief that their mass was consistent. Over time, carat weight became standardized and is now a common reference on diamond certificates, regardless of the certifying institution.

Diamond carat size comparison

While each diamond is unique, visual size can be approximated, especially since modern diamonds are machine-cut for precision. Within every carat range, diamonds have an average size in millimeters.

Round diamonds, if well-cut, have less depth than well-cut fancy-shaped diamonds (non-round diamonds). For instance, a 1ct round diamond has a length/width of ~6.40mm, while a 1ct Princess diamond measures ~5.50mm.

Fancy shapes tend to weigh more and be smaller in size. Consequently, round-cut diamonds cost more than fancy shapes of the same carat weight.

Visually, diamonds with a 5 to 10 percent carat weight difference are hard to distinguish. For example, a 0.95ct and 1ct diamond appear nearly the same, a notable point if you desire a 1ct diamond but not its price.

A deeper cut diamond may appear smaller than a lower-carat diamond. Thus, it’s essential to consider both carat weight and millimeter size, along with length-to-width ratios for each diamond shape. A deeply cut 1ct diamond might look smaller than a 0.95ct shallow-cut diamond.

Remember: Carat is a weight measurement, and a diamond’s millimeter size varies based on its cut. Opt for well-cut diamonds with less depth and more spread, making them appear visually larger than their carat weight.

Diamond MM Chart

Carat price effect: What does a diamond carat cost?

Diamond pricing escalates exponentially as carat weight increases. Once a diamond reaches its critical weight, the price surges. These 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, and 10.00ct.

Diamond cutters strive to keep the weight at or above each critical weight. Diamond manufacturers and suppliers are aware of this, so they price their diamonds accordingly. It might be smart to select a 0.95ct diamond instead of a 1 carat, but the former can be hard to find. (Fortunately, at Artful Bracelets, our expert gemologists can help you find the right stone in the right carat size.)

CARAT PRICE FOR LAB GROWN DIAMONDS

If working within a specific budget, consider lab-grown diamond comparisons. Lab-grown diamonds share the same physical, chemical, and optical properties as natural diamonds, differing only in their creation (earth vs. laboratory). Below is a table comparing the prices of round natural and lab diamonds.
View the certified lab diamond catalog.

Diamond Carat and Price

NATURAL DIAMONDS VS LAB DIAMONDS (BASED ON ROUND SHAPES)

Values are estimated and can vary based on our inventory.

UNDERSTANDING “MAGIC SIZES”

By understanding “magic sizes” — popular weights that command higher prices — you can save a significant amount on your engagement ring. Although there’s no visual difference between a 1.99ct and a 2.00ct diamond, the latter costs more due to its “magic size.” Diamonds that aren’t these “magic sizes” are termed “off-size diamonds,” which might just help you secure your dream engagement ring at a better price.

What is the average diamond carat weight?

The average diamond carat weight is 0.90ct.

Consider purchasing a diamond just below the critical weight, such as 0.95ct vs. 1ct, as prices rise significantly at these critical points.

How important should carat be when buying a diamond?

Due to its high visibility, carat is often seen as the most important of the 4 C’s. Some buyers may prioritize carat weight; however, we suggest considering diamond cut first, although this depends on personal preference. Carat weight is significant but must be balanced with the other factors.

When pricing diamonds, balance carat weight against the remaining 3 C’s —
cut,
color,
clarity. You might need to compromise on the other C’s if you increase carat weight to stay within budget. Conversely, you may need a lower carat if you prioritize the other qualities. A higher carat diamond occupies more space on the hand, but without optimizing for cut and clarity, it won’t sparkle as much.

Use our diamond price estimator to get an approximate pricing range based on various diamond sizes and attributes.

Diamond carat sizes on hand

Below, you can observe how different diamond carat sizes appear on a hand. Consider her hand and finger size when shopping. Fancy shapes like emerald, oval, and pear will often look larger than a round diamond of the same carat weight. Learn more about various
diamond shapes to choose the perfect one for her ring. Also, keep in mind that certain ring styles can make the diamond carat weight look even larger once set within the ring.

Below are round diamonds of 0.25ct, 0.50ct, 0.75ct, 1.00ct, 2.00ct, 3.00ct, 4.00ct, and 5.00ct respectively.