Beyond the 4Cs: Diamond Measurements

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Don't get caught up in the carat count when you're shopping for the perfect diamond. It's not just the carats, but things like shape, cut precision, and length-to-width ratio of a diamond that determine its quality - and beauty.
While carats are a significant consideration, they don't tell the whole story. The true beauty and impact of a diamond are shaped by the 4Cs, including its clarity, color, and the all-important cut. These elements work together harmoniously to create a diamond that captivates with its brilliance and elegance.
Getting to know the intricacies of diamond measurements is crucial, since each aspect can greatly affect the stone's appearance. There’s a lot that goes into how the diamond carries its weight and, subsequently, how it appears to the eye.
To illustrate how the measurements of round cuts, princess cuts, oval cuts, and emerald cuts correlate to carats, we have outlined their measurements below and gone into detail about their appearance.

An Intro To Carats and Diamond Measurements Size

Carats are units used to measure diamonds, but many are unaware that carats measure weight, not size. While carat weight affects how your diamond looks, it does not directly correlate with size. In fact, two diamonds of the same carat can appear very differently depending on how they carry their weight.
Round Diamond Carat Weight Chart
A diamond's size is described in millimeters (mm) and these measurements are roughly comparable to carats in round diamonds.
Typically, a 1-carat round diamond measures 6.4 mm, while a 1.25-carat round diamond measures 6.9 mm. For comparison, square-cut diamonds like princesses, cushion cut diamonds, and asscher cuts are typically 5.5 mm, and 1.25 carats are 6 mm. Typically, fancy shapes like ovals, emeralds, pear-shaped diamonds, and marquises are described by their length and width, but there are some measurements to go by.
In addition to giving the diamond a poor appearance, poor cutting can conceal additional weight beneath its girdle, which is usually covered by the ring. A poorly cut 1.25 ct. round diamond, for instance, may appear similar in size to a well cut 1 ct. round diamond. In addition to appearing smaller, they will also be deficient in optical performance.
Elongated fancy-shaped diamonds with shallower depths and longer dimensions can take up more real estate on a finger or in a ring than classic round diamonds. This finger coverage is one of the reasons why some shoppers choose elongated shapes such as marquise and oval.

Length to Width Ratio

Length to width ratio is a crucial aspect of diamond proportions that determines the overall shape and aesthetics of a diamond.
The ratio is calculated by dividing a diamond's length by its width and is applicable to various diamond shapes, be it round, square, oval, or rectangular. For round and square diamonds, the ideal ratio hovers around 1.0, as these shapes should exhibit near-identical length and width dimensions.
However, when it comes to rectangular and oval-shaped diamonds, the game changes. The most appealing ones tend to be longer than they are wide, with ideal length to width ratios ranging from 1.25 to 2, depending on the cut (shape).

Diamond Proportions and Appearance

The depth percentage is a diamond's depth divided by its diameter, and it plays a vital role in determining a diamond's performance and visual appeal. Diamonds with low depth percentages, often short and wide, may seem larger but tend to lack the ability to reflect light effectively, resulting in a somewhat lackluster appearance.
Conversely, high depth percentages characterize tall and wide diamonds, which frequently appear dull due to light escaping from the diamond's bottom instead of returning to the eye. To ensure maximum sparkle and brilliance, it's advisable to select a diamond within depth percentage ranges appropriate to its shape.
Similarly, a diamond's table, the flat facet on top, is important to its sparkle. The table percentage is calculated by dividing a diamond's table width by its diameter, and it governs how light enters and refracts within the diamond. Optimal table percentages vary depending on the diamond's shape.
These measurements collectively play a vital role in determining a diamond's overall beauty and should be considered carefully when choosing the perfect gem for your jewelry.
To summarize, carat weight is only an indirect indicator of how large or small a diamond will appear. To ensure you get the best value for your money, all diamonds at Whiteflash, both natural and lab grown, are listed with detailed specifications including weight, measurement, cut quality, and performance imaging.

Round Cut Diamonds Measurements: MM To Carat Conversion Chart

The round cut diamond remains the most popular choice when it comes to fine jewelry. There is a long and rich history behind the iconic round cut diamond, which diamond cutters and experts have studied and refined over time to enhance its brilliance, scintillation, and fire.
Known for its outstanding beauty and sparkle, this shape remains a classic and popular choice.
As with any circle, a round brilliant diamond has approximately the same diameter all the way around. An imaginary line connecting two points on the stone's girdle, seen when looking at it from above, determines the stone's diameter.
This chart helps you understand how round cut diamonds are measured in millimeters (mm) and their respective carat weights:
Round MM Size
Round Carat Weight
 
0.8 mm.
0.0025 ct.
1 mm.
0.005 ct.
1.1 mm.
0.0067 ct.
1.2 mm.
0.009 ct.
1.25 mm.
0.01 ct.
1.5 mm.
0.015 ct.
1.75 mm.
0.02 ct.
1.8 mm.
0.025 ct.
2 mm.
0.03 ct.
2.2 mm.
0.04 ct.
2.5 mm.
0.06 ct.
2.75 mm.
0.08 ct.
3 mm.
0.10 ct.
3.25 mm.
0.14 ct.
3.5 mm.
0.17 ct.
3.75 mm.
0.21 ct.
4 mm.
0.25 ct.
4.25 mm.
0.28 ct.
4.5 mm.
0.36 ct.
4.75 mm.
0.44 ct.
5.0 mm.
5.25 mm.
0.56 ct.
5.5 mm.
0.66 ct.
5.75 mm.
6 mm.
0.84 ct.
6.25 mm.
0.93 ct.
6.4 mm.
6.9 mm.
1.25 ct.
7 mm.
1.30 ct.
7.3 mm.
7.5 mm.
1.67 ct.
7.75 mm.
1.75 ct.
8.1 mm.
8.25 mm.
2.11 ct.
8.5 mm.
2.43 ct.
8.8 mm.
9.1 mm.
2.75 ct.
9.4 mm.
9.6 mm.
3.35 ct.
9.8 mm.
3.61 ct.
10.1 mm.
3.87 ct.
10.25 mm.
10.5 mm.
4.41 ct.
10.75 mm.
4.57 ct.
11 mm.
11.25 mm.
5.49 ct.
11.5 mm.
5.85 ct.
12 mm.
6.84 ct.
12.25 mm.
7.26 ct.
12.5 mm.
7.36 ct.
12.75 mm.
7.52 ct.
13 mm.
8.51 ct.
13.5 mm.
9.53 ct.
14 mm.
ROUND CUT DIAMONDS
1.088 ct F VS1 Round Ideal diamond
1.088 F VS1 Round Ideal
A CUT ABOVE®
$8,650
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Eye Clean
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1.098 ct F VS1 Round Ideal diamond
1.098 F VS1 Round Ideal
A CUT ABOVE®
$8,675
Light Perf.
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1.107 ct F VS1 Round Ideal diamond
1.107 F VS1 Round Ideal
A CUT ABOVE®
$8,750
Light Perf.
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Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
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Fluorescence
Eye Clean
View Details
1.108 ct F VS1 Round Ideal diamond
1.108 F VS1 Round Ideal
A CUT ABOVE®
$8,750
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
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Fluorescence
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Princess Cut Diamonds Measurements: MM To Carat Conversion Chart

The princess cut diamond blends classic diamond sparkle with a contemporary angular silhouette, resulting in a diamond that has both a modern look and classic performance. Originally introduced in the 1960s, it is a relatively recent addition to the diamond shape menu.
With brilliance, scintillation and something truly different, the princess cut is one of the most popular fancy shapes. Diamonds with princess facet arrangements are described as rectangular or square modified brilliant cuts because of their similar faceting patterns.
In comparison with round carats, princess carat weights can be somewhat misleading as to visual size because of the dimensions used to communicate them. A round's footprint or "spread" is largely determined by its depth percentage, which is based on its depth, diameter, and girdle thickness.
In calculating the dimensions and depth percentage of a princess cut diamond, we use the smallest width to total depth ratio. This results in a relatively greater depth measurements and smaller diameters. Due mainly to this method of calculation, many people tend to think princess cuts look smaller than comparable weight in rounds.
An average 1ct round cut diamond measures approximately 6.5mm in diameter, whereas a princess cut diamond measures around 5.5mm, but the princess has more surface area than what the measurement suggests because it is taken at its smallest diameter. We’ve provided a conversion chart below to help you visualize the numbers below.
Princess MM Size
Princess Carat Weight
 
1.5 mm.
0.015 ct.
1.75 mm.
0.03 ct.
2 mm.
0.06 ct.
2.25 mm.
0.08 ct.
2.5 mm.
0.10 ct.
2.75 mm.
0.13 ct.
3 mm.
0.18 ct.
3.25 mm.
0.26 ct.
3.5 mm.
0.29 ct.
3.75 mm.
0.31 ct.
4 mm.
0.39 ct.
4.25 mm.
0.44 ct.
4.5 mm.
4.75 mm.
0.64 ct.
5 mm.
5.25 mm.
0.90 ct.
5.5 mm.
5.75 mm.
1.11 ct.
6 mm.
1.25 ct.
6.25 mm.
1.39 ct.
6.5 mm.
6.75 mm.
1.75 ct.
7 mm.
7.25 mm.
2.01 ct.
7.5 mm.
7.75 mm.
2.74 ct.
8 mm.
8.25 mm.
3.24 ct.
8.5 mm.
3.67 ct.
8.75 mm.
9 mm.
4.12 ct.
9.5 mm.
9.75 mm.
5.36 ct.
10 mm.
5.62 ct.
10.25 mm.
5.76 ct.
10.5 mm.
5.99 ct.
11 mm.
7.44 ct.
11.5 mm.
9.44 ct.
12 mm.
There is certainly a difference in aesthetics and flavor, but due to the math used in the calculations, the disparity in size is not as great as it appears on paper. And princess cuts are usually much less expensive than rounds of comparable quality and weight.
PRINCESS CUT DIAMONDS
0.700 ct I SI1 Princess Ideal diamond
0.700 I SI1 Princess Ideal
A CUT ABOVE®
$1,195
Light Perf.
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Eye Clean
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0.706 ct G VS1 Princess Ideal diamond
0.706 G VS1 Princess Ideal
A CUT ABOVE®
$1,495
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Star
Pavilion Angle
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0.753 ct G VS2 Princess Ideal diamond
0.753 G VS2 Princess Ideal
A CUT ABOVE®
$1,465
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Star
Pavilion Angle
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0.876 ct J SI1 Princess Ideal diamond
0.876 J SI1 Princess Ideal
A CUT ABOVE®
$995
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
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Fluorescence
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Oval Cut Diamonds Measurements: MM To Carat Conversion Chart

Oval cut diamonds are renowned for their elegant and elongated shape, which offers a unique twist on traditional round diamonds. They are known for their ability to create the illusion of longer, slender fingers when worn as engagement rings or other jewelry pieces.
The oval combines the classic brilliance of the round cut with an elongated silhouette, making it a favored choice among those seeking a more distinctive diamond shape. We have thoroughly compared round versus oval diamonds in detail in this blog, allowing you to make a confident choice with no regrets!
Oval diamonds are characterized by their elliptical shape, which can vary in terms of length-to-width ratio. The choice of ratio affects the overall appearance of the diamond, allowing customers to select the oval shape that best suits their personal preferences.
Here is a conversion chart that translates the millimeter (mm) size of oval cut diamonds into their respective carat weights, helping you better understand the dimensions and carat value of these exquisite gems:
Oval MM Size
Oval Carat Weight
 
3.6x2.7 mm.
0.10 ct.
4x3 mm.
0.15 ct.
4.5x3.5 mm.
0.20 ct.
5x3 mm.
0.25 ct.
5.5x3.5 mm.
0.33 ct.
5x4 mm.
0.35 ct.
6x4 mm.
6x5 mm.
0.61 ct.
6.5x4.5 mm.
0.65 ct.
7x5 mm.
7.7x5.7 mm.
8x6 mm.
1.25 ct.
9x6 mm.
1.41 ct.
8.5x6.5 mm.
9x6.5 mm.
1.75 ct.
9x7 mm.
10x8 mm.
10.5x8.5 mm.
2.88 ct.
12x8 mm.
12x8.5 mm.
3.50 ct.
11x9 mm.
3.85 ct.
12.5x8.5 mm.
12.75x8.5 mm.
4.50 ct.
12x10 mm.
14x10 mm.
5.81 ct.
13x11 mm.
6.05 ct.
14x12 mm.
8.21 ct.
15x12 mm.
8.76 ct.
16x12 mm.
OVAL CUT LAB GROWN DIAMONDS
1.00 ct D VVS1 Oval Ideal lab diamond
1.00 D VVS1 Oval Ideal
Precision Lab Diamond
$975
Light Perf.
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Measurements
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Eye Clean
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1.01 ct D VVS2 Oval Ideal lab diamond
1.01 D VVS2 Oval Ideal
Precision Lab Diamond
$950
Light Perf.
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Table %
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Star
Pavilion Angle
Crown %
Lower Girdle
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Eye Clean
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1.01 ct E VVS2 Oval Ideal lab diamond
1.01 E VVS2 Oval Ideal
Precision Lab Diamond
$895
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
Measurements
Fluorescence
Eye Clean
View Details
1.01 ct D VS1 Oval Ideal lab diamond
1.01 D VS1 Oval Ideal
Precision Lab Diamond
$750
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
Measurements
Fluorescence
Eye Clean
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Emerald Cut Diamonds Measurements: MM To Carat Conversion Chart

Emerald cut diamonds are celebrated for their timeless elegance and sophisticated, rectangular shape. This diamond cut, known for its step-cut facets and open table, offers a unique and understated light performance that sets it apart from other diamond shapes.
The emerald cut is favored for its ability to showcase a diamond's clarity and color, making it a preferred choice for those who appreciate the beauty of a pure and transparent gem. Its elongated shape and horizontal step-like faceting is often associated with grace and sophistication.
From the square Asscher shape to elongated emerald cuts, the overall shape of an emerald cut can vary significantly. Personal taste plays a large role in the shape's outline. There are some who prefer a long, slender shape, while there are others who prefer a wider rectangle.
The majority of people prefer a rectangle with a length-to-width ratio of approximately 1.4. In order to ensure that you receive a top-quality emerald cut diamond, it is highly recommended that you work with a vendor that specializes in cut quality and who can provide comprehensive evaluations such as advanced light performance diagnostics that show how well a diamond handles light.
To assist you in understanding the relationship between millimeter size and carat weight for emerald cut diamonds, we present the following conversion chart:
Emerald MM Size
Emerald Carat Weight
 
3x2 mm.
0.10 ct.
3.5x2 mm.
0.12 ct.
4x2 mm.
0.15 ct.
4x3 mm.
0.20 ct.
4.30x3 mm.
0.25 ct.
5x3 mm.
0.29 ct.
5.5x3.5 mm.
0.46 ct.
6x4 mm.
6.5x4.5 mm.
6.7x4.5 mm.
0.88 ct.
7x5 mm.
7.3x5.3 mm.
1.25 ct.
7.5x5.5 mm.
8x6 mm.
1.75 ct.
8.5x6.5 mm.
9x7 mm.
9.3x7.5 mm.
9.5x7.5 mm.
3.21 ct.
9.75x7.7 mm.
3.50 ct.
9.9x7.8 mm.
3.79 ct.
10x8 mm.
10.5x8.5 mm.
4.50 ct.
11x9 mm.
12x8 mm.
5.34 ct.
12x10 mm.
6.00 ct.
14x8 mm.
6.25 ct.
14x9 mm.
6.38 ct.
14x10 mm.
8.48 ct.
13x11 mm.
EMERALD CUT LAB GROWN DIAMONDS
1.01 ct D VVS2 Emerald Ideal lab diamond
1.01 D VVS2 Emerald Ideal
Precision Lab Diamond
$880
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
Measurements
Fluorescence
Eye Clean
View Details
1.01 ct D VVS1 Emerald Ideal lab diamond
1.01 D VVS1 Emerald Ideal
Precision Lab Diamond
$975
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
Measurements
Fluorescence
Eye Clean
View Details
1.02 ct D VVS2 Emerald Ideal lab diamond
1.02 D VVS2 Emerald Ideal
Precision Lab Diamond
$895
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
Measurements
Fluorescence
Eye Clean
View Details
1.06 ct D VVS1 Emerald Ideal lab diamond
1.06 D VVS1 Emerald Ideal
Precision Lab Diamond
$995
Light Perf.
Polish
Symmetry
Depth %
Table %
Crown Angle
Star
Pavilion Angle
Crown %
Lower Girdle
Measurements
Fluorescence
Eye Clean
View Details
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Find Your Ideal Diamond with Whiteflash

The size of the center stone should not be the only consideration when choosing a diamond for an engagement ring. The process of choosing an engagement ring should be enjoyable, not stressful, which is why we provide guides for other popular ring sizes as well:
We also offer personal consulting services here at Whiteflash, so you can shop with confidence knowing our diamond experts are here to assist you. Everyone has their own criteria and budget that they are working with. That's why we customize your experience to fit your needs.
Our inventory of loose diamonds in a variety of shapes and our in-house A CUT ABOVE® range of super ideal cut diamonds are the perfect centerpieces for our beautiful collection of designer settings. You can create a truly unique and breathtaking piece of jewelry with these settings, which have been carefully selected to complement our diamonds and enhance their beauty.
While fine natural diamonds can be very to extremely expensive as the carat weight increases, the recent availability of high quality laboratory grown diamonds represents a great opportunity for some shoppers to own a high quality diamond at a very affordable price.
Lab grown diamonds are real diamonds with essentially the same chemical, physical, and optical properties of natural diamonds. But instead of having been created over billions of years deep within the Earth, lab grown diamonds are produced in factories over a few days or weeks, making them much more affordable.
Any lab grown diamond with top color and clarity that has been cut with precision for outstanding optical performance will rival the majority of natural diamonds available in terms of beauty. Whiteflash offers such diamonds in our Precision Lab brand.
Lab-grown diamonds of this quality represent the best available. In light of the significantly lower cost basis, there is little reason to compromise on color, clarity, or the all-important cut. And opting for a fine lab grown diamond can offer the opportunity to step up to a fine designer brand setting and stay within a reasonable budget.
With the help of our fully functional website and knowledgeable diamond consultants, you will be able to visualize and fully understand the diamonds that capture your eye. Your satisfaction and confidence are our top priorities, and we're honored to be a part of your jewelry shopping experience.
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