Round vs. Princess Cut: Key Differences

Out of the 4Cs of diamond quality, the cut is the C that should be emphasized to get the best light reflection and refraction. Several modifications to the round cut design have occurred over the years. It was formally called the circular brilliant cut, and later, in the 1950s, became the modern round brilliant as it is currently known. In all these phases, the proportions of the cut varied significantly, giving the diamond a different face-up pattern. Each stage of cut development resulted in an improved facet pattern and light performance. The average number of facets on a round brilliant cut is 57 or 58 when the round cut has a culet. The modern round cut has a larger table and longer pavilion facets compared to earlier versions. Table 1 below shows the ideal measurements of the various parts of a round cut stone.

Table 1. Chart of the Depth, Table, and Other Percentages for a Round Cut

Cut	Table (%)	Depth (%)	Crown Angle	Pavilion Depth	Girdle	Culet	Length to width Ratio
Excellent	53 - 58	59 - 62.3	34 - 34.9	42.8 - 43.2	Thin to Slightly Thick	None	1.00 - 1.01
Very Good	52 - 53 or 58 - 60	58 - 58.9 or 62.4 - 63.5	32.1 - 33.9 or 35 - 35.9	42 - 42.7 or 43.3 - 43.9	Very Thin to Slightly Thick	Very Small	1.00 - 1.01
Good	51 or 61 - 64	57.5 - 57.9 or 63.6 - 64.1	30.1 - 32 or 36 - 37.9	41 - 41.9 or 44 - 45.5	Very Thin to Thick	Small	1.00 - 1.01
Fair	50 or 65 - 69	56.5 - 57.4 or 64.2 - 65	29 - 30 or 38 - 40.5	39 - 40.9 or 45.6 - 48	Very Thin to Very Thick	Medium	1.02
Poor	< 50 or > 69	< 56.5 or > 65	< 29 or > 40.5	< 39 or > 48	Extremely Thin to Extremely Thick	>Medium	> 1.02

To grade the round cut, the GIA has a system specifically for unmodified round cut stones. It ranges from excellent to poor cut. An excellent round cut would be the best value for money when buying a round cut stone. The very good or good cut are workable alternatives and will get you a diamond with above-average brilliance and fire. Whereas the round cut is characterized by smooth rounded edges throughout, the princess cut has sharp corners. It has a square shape, hence the likening to the base of an inverted pyramid. Being a square-shaped stone means it has pointed, sharp corners susceptible to chipping. You can chamfer the corners for a smooth edge but risk affecting brilliance. Therefore, you will be better off leaving the stone intact and being cautious with it instead. Unfortunately, the GIA has no cut grading scale for princess cut diamonds. For princess cut analysis, the AGS proportions and light performance grading system outweighs the rest of the grading criteria. To get insights on the ideal dimensions of a princess cut stone, see Table 2 below.

Table 2. Chart of the Depth, Table, and Other Percentages for a Princess Cut

Cut	Table (%)	Depth (%)	Girdle	Culet	Length to width Ratio
Excellent	67 – 72	64 – 75	Very Thin - Slightly Thick	None	1.00 - 1.03
Very Good	59 - 66 or 73 - 75	64 – 75	Very Thin - Slightly Thick	Very Small	1.00 - 1.03
Good	56 - 58 or 76 - 82	58 - 63.9 or 75.1 - 80	Very Thin to Thick	Small	1.04 - 1.05
Fair	53 - 55 or 83 - 85	56 - 57.9 or 80.1 - 84	Very Thin to Very Thick	Medium	1.06 - 1.08
Poor	< 53 or > 85	< 56 or > 84	Extremely Thin to Extremely Thick	> Medium	> 1.08

The clarity of round and princess cut diamonds refers to the blemishes or inclusions on the stone - not all inclusions are bad. For instance, some small traces of clouds are natural and do not affect the stone's clarity. However, dark spots are a sign of low clarity quality. According to the GIA, a round cut stone can be either flawless (FL) with no inclusions and blemishes or included (I) with a concerning level of inclusions. Between these two extremes are clarity grades that may or may not be visible to the naked eye. We recommend that you get an eye-clean round cut diamond, such as a VVS2 or VS1 round diamond, that could appear similar in clarity even when put before experts. But under 10X magnification or higher, the former (VVS2 round diamond) has fewer inclusions compared to the latter (VS1 round diamond).

The exact location of the blemish is also crucial. For the round cut, blemishes on the girdle are not visible from an aerial view of the table. It is more challenging to spot them in a ring due to the obstruction of the stone by prongs. Defining clarity in the princess cut can be difficult, though it is good when the intention is to hide the blemishes. The princess cut is the round cut’s runner-up in brilliance and luster. Its impeccable light performance and pointed corners enable it to emit color from the center and edges. The result is a versatile coloration, which could make it hard to spot blemishes and inclusions. It is a downside if you are a naive buyer and a dishonest jeweler pulls this trick on you. The stone could be eye-clean but have clarity of I1, further down the clarity scale. If the inclusions appear on the corners of the stone, it is an issue that makes the stone prone to chipping. Flawless or internally flawless princess cut stones are rare. Settling for a princess cut diamond between VS1 and S1 would be an excellent choice. The stone’s price would be friendly or reasonable at that clarity quality. But cut and color must also be optimal to consolidate your budget purchase.

When it comes to color grading, the GIA color scale does a great job of simplifying the coloration analysis. The color scale used in GIA labs has 23 color classifications symbolized by alphabetical letters D to Z. D represents a colorless diamond. Z is the lower end of the color spectrum and signifies the presence of a yellow or brown tint in the stone. Round cut diamonds have superior light reflection over all other diamond shapes. For this reason, the perfectly proportioned facets of a round cut reflect light at appropriate angles in the pavilion. The superbly reflected white or colored light shoots through the table, supplying the highest levels of fire and brilliance. At this level of light performance, the round cut diamond’s color could be unnoticeable. That makes it difficult to distinguish between two adjacent colors on the scale. G and H colors, for instance, look similar unless you examine the stone under special lighting and compare it with master stones.

Colorless stones carry the highest market value. As a rule of thumb, color is a quality that you can compromise on to lower the price when buying a round cut. A color grade between G and J is near-colorless, and that should look good enough on a white or rose gold setting.

The princess cut displays a versatile color play from its center and in its corners, depending on the angle at which it is held against light rays. Its exact color can be elusive to a layman. H and I colors are recommended for a princess cut. Another aspect to check with round and princess cuts is fluorescence since it explicitly affects color and not the other 3Cs. Fluorescence is the blue glow that diamonds produce under ultraviolet light. The brightness can be absent, faint, medium, or strong blue. It is terrible for purely colorless diamonds (D-F color). The blue glow compliments a yellow hue, making it suitable for H-Z color diamonds.

Round and princess cut stones are the most sought-after diamond shapes in the diamond industry. While both have a tremendous color display, the round cut beats the princess cut at brilliance. Round-cut diamonds also conquer all other cuts at light reflection and brightness. If you are in the market for a diamond, either of these cuts would be ideal for you. You may be spoiled for choice when it comes to round cuts.

Whether modified or not, you stand a high chance of getting a satisfactory round cut diamond because excellently cut round stones of faint or light color and SI2 clarity look flawless. Thanks to mathematically derived benchmarks and proportions, cutters can produce a round brilliant despite the size (say 0.5ct and below). But do not let the craftsmanship of the round cut make you skimp through princess diamonds. The princess cut has an edgier and more modern style to it. Check out the rectangular princess cuts first. They tend to be a bit cheaper than their square counterparts. The princess cut retains around 80 percent of the rough stone. It has a refractive quality, as good as the round cut. Therefore, you should get a princess cut if you fancy elaborate custom and vintage ring designs. It is your best bet at bringing out a lavish look.