How do I calculate Depth %

[Carlosthejakal]

Hi All,
The search for the perfect stone continues. Going to Antwerp this evening.
Round Stones
How do I calculate Depth % as HRD Certs dont display this.

I know its something to do with ratios ?
if it is related to the width & height of the diamond which width do I use
Smaller, larger or average of both ?

Example 7.23 - 7.27 x 4.56.

Any help would be appreciated.
Also what are the best percentages to look for ?

Thanks
Carlos

 

[Lorelei]

Try this thread. If this doesn't help then we will see if Sir John pops in as he is bound to be able to help, or some others.

http://niceice.com/calculate.htm

 

[Carlosthejakal]

yet again you come to my aid.

Thanks

 

[JohnQuixote]

Date: 4/23/2007 10:46:48 AM
Author:Carlosthejakal
Hi All,
The search for the perfect stone continues. Going to Antwerp this evening.
Round Stones
How do I calculate Depth % as HRD Certs dont display this.

I know its something to do with ratios ?
if it is related to the width & height of the diamond which width do I use
Smaller, larger or average of both ?

Example 7.23 - 7.27 x 4.56.

Any help would be appreciated.
Also what are the best percentages to look for ?

Thanks
Carlos

To get the depth percentage for a round brilliant you divide its depth in mm by its average girdle diameter.

Example: A round measures 6.48–6.52 x 3.95

First, get the average girdle diameter. Add the smallest and largest diameters (the first two mm numbers) and divide by two.

* Add the first two numbers (6.48 + 6.52 = 13.00)
* Divide by 2 (13.00 ÷ 2 = 6.50)
* Round to the nearest hundredth = 6.50

Second, divide depth (the third mm number) by the average girdle diameter you calculated and multiply by 100, rounding the result to the nearest tenth of a percent.

* Divide depth by average girdle diameter (3.95 ÷ 6.50 = 0.60769)
* Multiply by 100 (60.769)
* Round to the nearest tenth of a percent = 60.8%

With rounds, the greater the depth the smaller the diamond 'faces up' but the total configuration - especially crown and pavilion angles - determines performance. Cut grading systems used by the major labs generally include depths of 59-63% as candidates for the top grade. Other systems are more narrow but that range is solid ground.

 

[RockDoc]

Date: 4/23/2007 10:46:48 AM
Author:Carlosthejakal
Hi All,
The search for the perfect stone continues. Going to Antwerp this evening.
Round Stones
How do I calculate Depth % as HRD Certs dont display this.

I know its something to do with ratios ?
if it is related to the width & height of the diamond which width do I use
Smaller, larger or average of both ?

Example 7.23 - 7.27 x 4.56.

Any help would be appreciated.
Also what are the best percentages to look for ?

Thanks
Carlos

The total depth of the stone encompasses the crown height, the girdle thickness, and the pavilion depth.

The individual factors are important to know. Those can greatly affect how the diamond will look and return light.

For example

Stone 1

8% crown height - 5% girdle thickness and 47 % pavillion depth = 60%


Stone 2

14.5% crown height - 3.5% girdle 42% pavilion depth = 60%


Both stone have a 60% total depth but would be noticeably different.

Rockdoc