Question on calculating proportions

[dylanandtyler]

Hi all,

I'm new here and trying to figure out how the crown angles are calculated. I have the formula to 1.) divide the table by 100 2.) subtract this from 1 3.) multiply this by 50 4.) divide the crown depth by this figure 5.) press the tan-1 key on scientific calculator.

My question is, if you only need the table and crown height to figure out CA, wouldn't it stand to reason that say a 57% table and a 15.5% crown height would produce the SAME CA on every stone with these dimensions? Am I missing something? I see many stones with totally different CA with same dimensions.

I know numbers get rounded but I've seen CA's for those dimensions range from 35.1 all the way to 36.

Can any of you experts help me understand this?

Thanks

 

[DejaWiz]

There are multiple angles involved with crown facets. It isn't one uniform angle from girdle to table, so trying to calculate without taking an actual scan of the diamond may be an impossible task.

 

[dylanandtyler]

Thanks DejaWiz. That makes sense. So that "formula" cannot possibly be correct then.