When it comes to diamonds, carat is probably one of the attributes most often misunderstood as many believe carat refers to the size of a stone. In fact, carat refers to the weight of a diamond as opposed to its physical size, though the two are related. Beyond carat, a variety of factors can influence the apparent visual size of a diamond, including the diamond cut grade and shape of the stone. Together, these elements determine the price at which a diamond is sold to the consumer, whether natural diamonds or lab grown diamond alternatives. Understanding the influence of these factors will help you determine the best option for your budget for diamond alternative jewelry.

For carat size comparisons, it is easiest to see the differences when using a chart. One way to better understand it is to look at different shapes, like a round-cut diamond, and how they will visually appear at different carat sizes. Here is a helpful carat size chart to aid you in visualizing how a diamond’s shape and carat influence how its physical size appears.



Carat Size: 0.25 ct 0.50 ct 0.75 ct 1.0 ct 1.5 ct 2.0 ct 3.0 ct 4.0 ct 5.0 ct
Round 4.1 mm 5.1 mm 5.8 mm 6.4 mm 7.4 mm 8.1 mm 9.3 mm 10.2 mm 11 mm
Cushion 4x3.5 mm 5x4.5 mm 6x5 mm 6.5x55 mm 7.5x6.5 mm 8x7 mm 9x8 mm 10x8.5 mm 10.5x9 mm
Princess 3.5 mm 4.4 mm 5 mm 5.5 mm 6.4 mm 7 mm 8 mm 9 mm 9.5 mm
Oval 5x3 mm 6x4 mm 7.5x5.5 mm 8x5.5 mm 9x6 mm 10.5x7 mm 11.5x7.5 mm 13x8.5 mm 14x9.5 mm
Emerald 4.5x3 mm 5.5x4 mm 6x4.5 mm 6.5x5 mm 7.5x5.5 mm 8.5x6 mm 9.5x7 mm 10.5x7.5 mm 11.5x8.5 mm
Radiant 3.5x3 mm 5x4.5 mm 5.5x5 mm 6x5.5 mm 7x6 mm 7.5x7 mm 8.5x7.5 mm 9.5x8.5 mm 10x9 mm
Pear 5.5x3.5 mm 7x4.5 mm 8x5 mm 8.5x5.5 mm 10x6.5 mm 10.5x7 mm 12.5x8 mm 13.5x9 mm 15x10 mm
Asscher 3.7 mm 4.4 mm 5 mm 5.5 mm 6.4 mm 7 mm 8.1 mm 9 mm 9.6 mm
Marquise 6.5x3.3 mm 8.5x4 mm 9.5x4.5 mm 10.5x5 mm 12x6 mm 13x6.5 mm 14x7 mm 16x8 mm 17x8.5 mm
Trillion 4.9 mm 6.1 mm 7 mm 7.7 mm 8.9 mm 9.8 mm 11.2 mm 12.3 mm 13.2 mm

While carat is the standard unit of measurement, the millimeter measurement of a diamond tells you its true physical size. This is important when considering the faceting and shape because, as you can see in the diamond weight chart above, certain shapes will appear larger in size at equivalent carat weights. Oblong shapes specifically, such as emerald, oval, or pear, often look larger than their round counterparts. When shopping for diamonds, the carat weight, as well as millimeter measurements, can always be found on the Gemological Institute of America (GIA) certificate of the diamond.



Selecting a Diamond Size

Today, diamonds are often cut using special machinery, which can help eliminate a majority of possible imperfections. However, slight variations can be caused by inclusions or other natural factors within the diamond itself. The depth of the diamond can also impact its physical appearance from a face-up view, as is customary when in a setting. Working directly with a gemologist or other professional can help you ensure that you are getting the right size, as these experts will know the ideal proportions for a particular shape. You will most often find diamonds sold at certain cutoff weights or magic numbers as they are known within the industry. These weights occur at regular intervals such as 0.25-carats, 0.50-carats, 0.75 carats and so on.

A depiction of carat weight compared next to household items

A diamond's cut grade should also be considered. When a diamond is well cut, grading Very Good or higher, light is better reflected out of the top of the diamond, thereby making it appear larger. A smaller diamond with a better cut grade can appear larger than a bigger diamond with a poor cut grade.

It’s also critical to consider the diamond clarity and color when choosing a diamond’s size. Compromising on these two factors in an effort to purchase a larger diamond may not be the best choice because a larger diamond will more prominently display color or clarity flaws.



Impact of Carat on Price

After you have determined the cut, color and clarity grade of a diamond, you can easily use the carat weight to find the right diamond for your budget. In general, larger diamonds are much more expensive and valuable because they are discovered less frequently in nature than smaller ones. Despite popular belief, the natural diamond prices increase exponentially as carat weight increases, as opposed to linearly. This means that a 1-carat diamond is always valued higher than two 0.5-carat diamonds, even if all 3 are of the same quality. Generally speaking, a natural diamond of double the weight will cost approximately four times more than the smaller diamond.

Buying Tips

Purchasing a diamond can quickly become a significant investment. However, empowered with a few tips, you can easily find the diamond ring of your dreams that’s still within your budget.

Buy Shy. Typically, the price of a diamond jumps when you reach a new cutoff weight. Buying just below these weights can provide considerable savings with very little visual difference, thanks to the exponential pricing model. For example, selecting a 1.4-carat diamond rather than a 1.5-carat will look nearly the same in physical size but the price tag could be drastically different.

Consider Depth. Diamonds that have less depth tend to have a larger spread, meaning their millimeter measurements are larger without adding carat weight. Finding these diamonds could mean that your 0.75-carat princess cut diamond looks more like a 1-carat at a lower cost.

Look at Fancy Shapes. Round diamonds tend to be one of the most popular shapes, and therefore tend to be priced higher due to market demand. Alternative options include fancy shapes, such as emerald, cushion, princess, oval, radiant, pear, Asscher, marquise and trillion.

Make Small Sacrifices. When it comes to clarity and color, choosing a diamond that has a slightly lower grade will have minimal visual difference, but can save you a lot in terms of cost. In fact, a gemologist is likely the only person that will be able to see the variation across the high end of the diamond color scale, with D, E and F diamonds. Those diamonds with G, H or I color grade may have slight tints of yellow that can usually only be detected when next to a diamond with a higher grade. The same is true for clarity grades. Slightly Included (SI) diamonds have imperfections that can only be detected at 10x magnification, as opposed to Very Slightly Included (VS) or Very Very Slightly Included (VVS). VS and VVS are difficult for even a trained professional to see under 10x magnification. These small trade-offs can help you find areas to reduce cost, while still purchasing a beautiful diamond in the size you desire.

Think Ring Size. Lastly, consider how a diamond will look on the finger of your future fiancée. A diamond may appear larger on a smaller finger than it does on a larger one. Additionally, the setting you select for the diamond can have an impact on how the size appears once worn on the finger.

Consider Diamond Alternatives. There is a multitude of options available in the fine jewelry market today beyond just natural, mined diamonds. The question, are lab diamonds real, can be answered by increasing your understanding of the different options. From lab grown diamonds to other diamond alternatives, these options each have unique qualities when it comes to cut, clarity, color and carat size. In general, diamond alternatives are more affordable no matter the carat size - lab grown diamonds may be up to 30% less than mined diamonds and options like Nexus Diamond alternatives will be up to 80% less than mined diamonds. Even with this cost savings, it is still important to evaluate the other quality factors when assessing an alternative diamond option. Nexus Diamond alternatives are created with a patented formula intended to simulate the look, weight and wear of a natural diamond, and at perfect quality. Every one of these diamonds will be completely colorless, IF rated and Ideal cut, in every carat size, thereby ensuring a brilliant diamond at every price point.



Finding the Perfect Diamond for You

A rose gold solitaire engagement ring from Diamond Nexus

Understanding how all of these factors work together to influence both the look and price of your diamond will help you select the right size stone for yourself or your loved one. If you combine the knowledge of your personal style and quality priorities with the expertise of the diamond carat chart, you will be poised to find the perfect diamond that is meant for you!



*Diamond Nexus strives to provide valuable information, while being clear and honest about our products. The Nexus Diamond™ alternative is a patented lab grown stone that, among all simulants, most closely imitates the look, weight and wear of a mined diamond, with two exceptions - it is absolutely perfect in every way, and it costs significantly less. Price points and environmental facts expressed in this blog were taken from popular online retailers and may vary. Learn more about the environmental impact of mining by visiting out blog: blog.