People often ask us what the optimum range is for the total depth of a princess cut diamond... The honest answer is "It's truly not that simple."

As much as we'd love to provide you with a simple formula for selecting a princess cut diamond which is going to be lively and vibrant, just as we do for round brilliant ideal cut diamonds, the fact of the matter is that the basic design and facet structure of a princess cut diamond is not symmetrical like it is for a round brilliant and thus the simple ratio of total depth = spread does not apply. To be clear, the term "spread" as it applies to diamond vernacular refers to the visible diameter of the diamond or how large the surface of the diamond "faces up" to the observer.

With a round brilliant cut diamond, the depth measurement is calculated as a percentage of the diameter, the result is a direct indication of the spread of the diamond. Generally speaking, the deeper the total depth measurement of the diamond, the less surface area that is visible to the observer. Quite simply a higher total depth measurement results in lower spread while a lower total depth measurement results in a higher amount of spread or visible surface. With round brilliant cut diamonds, a total depth measurement between 59 - 61.8% is considered to be an optimum range because it will result in proper spread, while something like 62.3% would result in less visible diameter... This is an important concept with round brilliant cut diamonds because it could mean the difference between buying a one carat diamond that faces up properly in the range of 6.50 millimeters in diameter (59 - 61.8% total depth) or one which faces up closer to 6.3 mm in diameter which is more like a 0.90 carat diamond. Since there is a substantial price increase which occurs between the 0.99 - 1.00 carat marks, it makes sense to buy a diamond with a spread or visible surface equal to the carat weight which you are paying a premium to achieve.

Unfortunately the well known and time tested methods for selecting a round brilliant ideal cut diamond "by the numbers" does not work for fancy shape diamonds in our experience. In fact, attempting to purchase a fancy shape diamond by the numbers is an easy way to be misled from both a technical and psychological perspective.