Ideal Round Cut Diamond Depth, Table, Proportions Guide

Executive Summary

The round brilliant diamond is a very brilliant diamond with 58 facets and an exceptional ability to reflect white light. The round brilliant cut has very thin facets, quite thinner than the old European cut that was common before its emergence.

In evaluating the quality of a diamond’s cut, you must ensure that the diamond is cut ideally, not too deep and not too shallow as well. When a round brilliant diamond is cut too deep, the light coming in will strike the pavilion at a very sharp angle. This prompts the reflection of the light to another pavilion and the light exits through the bottom of the diamond instead of being reflected through the top of the table. This is why a deeply cut diamond will be dull instead of being radiant.

When a diamond is cut ideally, each pavilion is struck by the incoming light and the light reflects back to the eye through the crown and the table. An ideally cut round brilliant diamond with optimal facet angles reflect both white and colored light flawlessly.

It is difficult to distinguish color in round cut diamonds. This is due to the high level of brilliance which they have. This masks the color in the diamond and allows you to buy go down the color grade. Depending on your setting, you can go as far down as the J, K or L grade.

Inclusions and blemishes are also not easily seen in round diamonds because of their brilliance. This allows you to settle for an SI1 instead of VVS1. This is how cut affects diamond clarity.

The shape of a diamond refers to the physical form or appearance of the diamond. It is important to note that there is a big difference between the shape of a diamond (explained above) and the cut of a diamond. There are different shapes or forms in which we can have diamonds. There are different diamond shapes with 10 of them being particularly common. They are the Oval, Emerald, Radiant, Round, Pear, Princess, Asscher, Heart, Marquise and Cushion shapes. The shape of the diamonds is important but they are not considered as part of the 4c’s used to evaluate a diamond which is the cut, color, clarity and carat weight. The most common of the different shapes of diamonds is the round cut diamond. It is so common that it is said to represent more than two third of all the diamonds that are sold. The round cut diamond has 58 facets and has a very high brilliance (it reflects white light very excellently) and has a cone-like shape. They are most often used as jewelry pieces such as necklaces, rings, etc.

The Round Brilliant Diamond Cut

This cut has 58 facets and is a very brilliant cut with an exceptional ability to reflect white light. The cut of a diamond is very important because it affects its ability to reflect light. When a diamond is cut to the right proportion, the light that enters from any direction is fully reflected from the top of the diamond. The light is then dispersed into a sparkling display. This is what is known as the brilliance of the stone.

What is known as the ‘ideal cut’ is a mathematical formula used to cut stones/diamonds into precise angles and proportions in order to get the optimum refraction and reflection of light rays. When a diamond has been ideally cut, light rays from the different sides are bent to the center of the stone and are reflected through the top of the diamond in a blaze of beautiful light. If the diamond has not been ideally cut, the light coming into it will leak out through the bottom of the diamond or the sides. So, the brilliance of a diamond has a lot to do with cutting the diamond ideally.

At the beginning of the 20^th century, Marcel Tolkowsky increased the interest in round cut diamonds after he published his work “Diamond Design: A Study of the Reflection and Refraction of Light in Diamond”. This highlighted the ideal way to cut a diamond, making use of its specific angles and proportions in order to maximize its brilliance. Since then, 1919, the round cut has been the most common diamond cut. The round brilliant cut has very thin facets, quite thinner than the old European cut that was common before its emergence. The tolkowsky specifications are 53 tables, 59.3 depth, 34.50 crown angle, and visible culet.

The quality of a cut determines how beautiful a diamond is. The quality of a round brilliant cut is graded by the GIA on a scale from poor to excellent:

Excellent – excellently cut round brilliant diamond provides the highest level of brilliance and fire. Almost all of all the light that comes in through it is reflected back through the table.
Very good cut – the majority of the light that enters into it is reflected back through the table and they offer a high level of brilliance and fire.
Good cut – this provides a lot but not an overwhelming brilliance. Much of the light that comes into it is also reflected through the table.
Fair cut – they offer little or minimal brilliance and a light goes out through the bottom and sides of the diamond.
Poor cut – they offer no spark or brilliance at all and light more easily escapes from the sides and bottom of the diamond.

When a round brilliant is cut too shallow, the light that is coming in will strike the pavilion at a very low angle. The light will then travel through the diamond and escape through the sides without being reflected through the top of the table to the eyes. The large amount of light that is able to escape causes the diamond to be dull, lacking both fire and brilliance.

The cut quality is the characteristic that impacts the beauty of the diamond the most, it is therefore very important to pay a lot of attention to this characteristic than the others especially when buying a diamond.

There are different cut grades for a round diamond. The table below shows GIA’s guideline for evaluating round diamond cut.

	EXCELLENT	VERY GOOD	GOOD	FAIR	POOR
Table	53-58	52 – 53 or 58 -60	51 or 65 – 69	50 or 65 -69	< 50 or >69
Depth	59-62.3	58 – 58.9 or 62.4 – 63.5	57.5 – 57.9 or 63.6 or 64.1	56.5 – 57.4 or 64.2 – 65	< 56.5 or > 65
Crown Angle	34-34.9	32.1 – 33.9 or 35 – 35.9	30.1 – 32 or 36 – 37.9	29 – 30 or 38 – 40.5	< 29 or > 40.5
Pavilion Depth	42.8-43.2	42-42.7 or 43.3-43.9	41 – 41.9 or 44 – 45.5	39 – 40.9 or 45.6 – 48	< 39 or > 48
Girdle	Thin to SI. Thick	Very thin to SI. Thick	Very thin to thick	Very thin to very thick	Ex. Thin to Ex. thick
Culet	None	Very small	Small	Medium	>Medium
L/W Ratio	1.00 – 1.01	1.00 – 1.01	1.00 – 1.01	1.02	> 1.02

Round Cut Diamond Color

The determination of a diamond’s color can be very tricky. It’s important to know these few things about the color of diamonds in general:

The overall value of a diamond depends a little on the absence of color.
There is a difference in the grade and value of diamonds between colored and colorless diamonds.
The setting of the ring can influence the view and perception of the color.
The color grade of a diamond should be determined only by a grading professional.

The GIA (Gemological Institute of America), a renowned diamond grading institute grades diamond based on their color into a diamond scale:

Grade D – F: Grade D is the highest diamond grade. The diamond nearly has no color. It appears colorless to the naked eye and under magnification. Grade E and F appear very identical to the naked eye. It’s almost impossible for the novice to identify the difference between these 3 grades, especially with the naked eye. Only an expert gemologist can accurately distinguish them. Diamonds in these grades D-F are usually set in white gold or platinum because yellow gold and other settings detract from the diamond’s uncolored beauty.
Grade G – J: these color grades also exhibits almost no color and are primarily colorless when viewed with the naked eye. They actually have tints of color but these diamonds should also be set in platinum or white gold. In order to reduce the effect of reflection of color from the yellow gold. These diamond are generally readily found that the D-F grade and can be found at a lower price point. The prices might reduce by about 10-15 as the grade reduces but the color difference might not be noticed with the naked eye.
Grade K – M: diamonds in these grades show a slight tint of yellow that can also be noticed by the naked eye. The diamonds can be set in a beautiful yellow gold setting. Due to the noticeable yellow tint of color, a diamond in these grades is usually sold for 50 less than those in the G-J grade.
Grade N – R: they have a noticeable yellow or brown color tint. These diamonds are available at a much lower price than the previous grades. Diamonds in these grades are not recommended for buyers.
Grade S – Z: diamonds in these grades have a very noticeable yellow or brow tinting. These diamonds cannot be recommended for diamond buyers.

When a diamond has that slight yellow or brown coloration, it reduces the amount of light that is reflected back to the eye. The more color it has, the less light it reflects and the more colorless a diamond are the more radiant, rare and valuable the diamond is.

The color of a round cut diamond is more difficult to distinguish because they reflect more light than other shapes of the diamond. The high level of its brilliance and the multiple facets that it has contributed to the difficulty in distinguishing its color, making the color a characteristic that should be carefully reviewed but not overemphasized. In considering the color of a diamond, the setting that is being used must be put into perspective. A diamond should appear colorless in relation to the setting that it is placed in. for instance, an I grade round cut looks colorless in a 14k white gold setting and a k colored diamond looks white in relation to its setting when placed in a 14k yellow gold setting.

It is advisable to use a white gold solitaire ring for a J grade diamond and yellow gold solitaire ring for K or L grade diamonds.

Generally, it is important that an expert views a diamond for its color before you go ahead and purchase it. Otherwise, it could cost you hundreds and thousands of dollars in purchasing an inferior grade diamond at a high price because you can’t distinguish the colors by yourself with the use of the naked eye.

Round Cut Diamond Clarity

The clarity of a diamond generally refers to the absence of blemishes or inclusions.

The GIA grades the clarity of a stone on a scale from the cleanest to the most included:

IF: Internally Flawless
VVS1: Very Very Small Inclusions 1
VVS2: Very Very Small Inclusions 2
VS1: Very Small Inclusions 1
VS2: Very Small Inclusions 2
SI1: Small Inclusions 1
SI2: Small Inclusions 2
I1: Inclusions 1
I2: Inclusions 2

Rather than reading the clarity grade of a diamond on a report, it is important to determine whether blemishes or inclusions can be seen with the naked eye. Check the diamonds without any magnifications and look if you will find any blemishes, dark spots or inclusions. In most cases, a VVS2 diamond will look the same as a VS1 diamond, they will both be free of inclusions when looking at them with the naked eye. Although it is identical to the eye, the price of VVS2 will be higher than VS1.

Apart from looking for the obvious blemishes, it is important to also note the location of the blemishes or inclusions. If they are seen around the perimeter of the diamond, it will be harder to see them through the table of the diamond. Once the diamond is set, the blemishes on the perimeter may be covered by the jewelry prongs.

However, it is generally recommended to make sure that the diamond doesn’t have any inclusions that can be seen with the naked eye. You do not need to look for a grade that is higher than this. What’s the point in paying for something that does not exactly make any difference? No one goes around with a magnification lens to view your diamond jewelry, isn’t it? If you find an S1 diamond with inclusions at the edge or perimeter, that are hard to notice or are covered by the jewelry prongs once set in a ring, you can go for that, rather than waste more money on a VVS1 diamond and no one notices the difference.

The clarity of a diamond can be affected by its cut. For example, inclusions or blemishes are not easily noticed in round cut diamonds. This means that the diamond clarity wouldn’t be as important for this type of diamond-like the color grade.

Round Cut Carat Weight

The seeds of carob pod were used in ancient times, as the standards for weight measurement because the size of the seeds was always identical. In 1907, when the fourth general conference on weights and measures held, it was agreed that the standard measurement for the modern diamond carat should be 200 mg. this is the standard diamond carat weight that is used generally today, it is known as metric carat. A diamond carat is a unit of weight and not size.

It is possible to have 2 diamonds of the same carat weight and the prices are not the same. This can be due to other factors like cut, color, and clarity. Generally, the price of a diamond will increase with an increase in the carat size. This is because the larger the size and weight of a diamond, the rarer it is to find. The more the carat weight of the diamond, the higher you will pay per carat weight increase.

Diamond carat weights are not a very important parameter in the sense that when you look at a diamond set in a ring, you can only see the physical dimensions, not the weight. The diamond is mostly covered in jewelry and it’s difficult to see the total physical size. All you really see is the size of the diamond’s surface area at the top. You can only estimate the importance of the carat weight in relation to you, your partner or whoever you are buying the diamond for. If the recipient wants a particular size of the diamond, carat weight can be useful to get a diamond within that size range. Otherwise, what’s the point in paying for something no one really sees or even pays attention to at all. When buying a diamond, the most important thing is the diamond’s cut. If it is ideally cut, you can look for other factors like the color. Always go for the lowest color, then go for the lowest clarity that appears very great to the physical eye. After these have been considered, go for the biggest diamond carat weight that fits well into your budget. The point is, carat weight should not be the first thing you are looking out for when buying a diamond. It’s actually the last you should check. You must make sure you find the balance between getting the best diamond that you can while ensuring that you’re not spending unnecessary money on carat size that no one sees or pays little or no attention to.

There is a correlation between the carat weight of a diamond and the diameter of the diamond. It is mathematically impossible for a 1 carat diamond to have less surface area than a 0.5 carat diamond. Due to the cut quality which can vary very greatly, there is a wide range of variation in the possible diameters for the particular carat weight. The cut of the diamond can affect the diameter of the round cut diamond.

The only other importance of the weight is that it determines the price that you are going to pay, but in making your valuations, you should be more particular about the cut grade of the diamond and its diameter. That informs your decision making when buying. After all, you will prefer to buy a 0.90ct diamond that is ideally cut, 6.2mm in diameter, looks beautiful and radiant cut and is still cheaper than a 1.00ct diamond that is poorly cut, with 6.1mm diameter and looks terrible. You can actually maximize your budget b buying shy. This means you can buy a diamond that is slightly below the whole carat mark and save some money. For example, you could buy a 1.9ct weight diamond instead of a 2.0ct weight. This will save you a lot of money and yet this slight difference of 0.1 would never be noticed by anybody.