weight and size for princess cut

[4quality]

I''ve seen this info for round as below:
ct wt dia (mm)
0.250 4.1
0.500 5.2
1.000 6.5
1.500 7.4
2.000 8.2
What is the ideal width for the above carat weight if it is a princess cut?

 

[valeria101]

Hm.. good luck finding the numbers...

Actually, it is not hard to find a set of measurements, but there is no "ideal" cut defined for princesses - so the numbers would vary quite a bit. The "ideal range" for rounds allows the depth of the cut to vary juts a few % points, but princess cuts are to be found in anything between 60% depth to 80% depth and no one yet agrees what exactly is an ideal range for them. Since the measurements of princess cuts cannot be translated into some prediction of light return (as is the case for "ideal" rounds), defining the 'ideal' princess is a tad more arbitrary.

You may want to consoder the existing industry standards (the AGA charts are an example of that) to decide what is your accepted range of measurements for princess cuts.

For example, teh AGA charts list 64% depth as the lowest in their top cut grade. I guess your sizes for rounds were taken for 60% depth (this is some kind of implicit standard, although some variation in depth would move those numbers either way) - a number both hard to find and not particularly desirable for princess cuts. In absence of optic analysis, on average, princess cuts as shallow as the ideal rounds would not achieve acceptable light return (at least this is the general assumptions I am aware of, which has not yet been challenged by an analysis of the optical properties of the cut model - again, as far as I know).

With some guessing involved, below are the respective side measues for square princess cuts at 65% depth.

Princess cuts at 65% depth
cts side length (mm)
0.25 3.5
0.5 4.5
1 5.7
1.5 6.6
2 7.3

 

[researcher]

I know this is an old post, but I was wondering if AnA or anyone else could tell me how you determine the "appropriate" diameter for a princess stone (in other words, how were these numbers determined). I just find this all so fascinating!

 

[Garry H (Cut Nut)]

You can easily do a search of the data base and find the real average LXW for say all the 1ct stones in round and the same for princess cuts.

Those quoted round widths are exaggerated, thin girdles and large tables give those #'s, not ideal cut stones.
.25 usually = 4.00mm in the real world, and 5.00 to 5.1 for 1/2ct.

When comparing face up spread for rounds and princess, well cut rounds have a larger surface area, and in addition rounds appear larger because they return more light.

I believe this could be shown in side by side comparisons with real photo's.

I have done a small survey and comfirmed this.

If you want a bigger look - go for marquise, ovals and pear shapes.

 

[researcher]

Thanks for your input, Gary!
I've actually already chosen a BEAUTIFUL 3.22 ct princess cut stone that scored VH-VH-VH on the BS. Even though most people in the business don't seem to like princesses as much as rounds, those who have seen my stone (including our independent appraiser) have said that mine is an exceptional performer. As someone who really isn't a fan of rounds (I have lots of them that have passed down in the family so I really wanted something different for my e-ring), I was just curious how AnA was able to determine the "ideal" diameters for princesses. Although I've chosen my e-ring stone, I'm now looking to purchase 5-7 .25 ct stones for a shared-prong wedding band and I just like working with numbers to get me started (and I work with numbers daily so am just curious as to the formula).

 

[valeria101]

----------------
On 5/30/2004 12:54:41 PM researcher wrote:



I was just curious how AnA was able to determine the 'ideal' diameters for princesses.

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Nothing ideal about those: I am affraid the numbers were deduced as Garry says. Using the formula for the volume of the respective prism I am getting pretty big errors, so I ditched that kind of exercise

Usually, a seller of such sets of matched stones will state a size for the weight (like DCD does HERE)...


The (not that useful) formula was:

0.0176 x Length square x [ total depth + crown height% x table% x (1 + table % square )]

where 0.0176 is diamond density in carats per cubic milimeter (from 3520 kg/m3) and "Length" is the length of the side for a square piece or the geometric average of length and width for a rectangular one....

 

[researcher]

Thanks for responding! I had tried the formula for volume as well, and realized it was completely off which is what got me wondering what you were using. It definitely makes sense, but I see now how it's completely an estimation And thanks for the tip on matching side stones--I had seen them on DCD but just wanted to know a little more about their matching process and whether I could make a good comparison on my own