how do you convert?

[Graham]

often when I am looking at diamonds they give you the dimensions like 4.29 X4.35 X 2.45
I just made these up, but is there a calcualtion you can run with these numbers and get an accurate table % and depth etc..I am confused at what these mean. also, I am looking to purchase an engagement ring and I have posted a few posts this week and am just throughly impressed with the imput I have received, this forum is fantastic! thanks to all that have responded.

 

[pricescope]

Graham,You only can get the diameter and total depth % from the measutrements.In your example an overage diameter is 4.32 and total depth = 2.45/4.32 = 57%

 

[jamesd]

You could try the cut class 1b parameters from the tutorial links. That should get you something which is attractive and which may not have too bad a premium.

 

[Graham]

so the 57% isthe depth, but I cant get the table %? how do I figure that out if they dont show it?can you give me ranges to stay within for a normal cut 58 facet diamond, I am not looking for "super ideals" as I am not rich, however I would prefer to buy a good stone that she will be proud of. looking to purchase a 1.25C stone and have about
$7500, jareds has given me 3000K of credit so I will probable purchase it there, but they have all IGI stones, they will get a GIA cert but want 300$ for that service, if I could find out the measurements from the numbers and use my eyes as a judge for sparkle and brillance I think I can pretty much grade the diamond myself. I am trechnical, I am an engineer and can do math pretty well, just new to diamonds.so I guess my follow up is
7500$ 1.25c, is that possible with good measurements, and how can I figure out the table, I know I have asked alot here but you seem so knowledgeable.thanks

 

[pricescope]

The table size should be on the grading report along with other cut data (girdle, symmetry, polish, and culet). It also would be great to get crown and pavilion angles.Check the tutorial on this site regarding cut. If you'd have the table%, depth% and crown & pavilion angles you could use Holloway Cut Adviser to evaluate the cut.If the diamond has no grading report your jeweler should get it for you. You also can use an independent gemologist/appraiser service to get you the cut information and verify that diamond is as represented.You might ask the jeweler to pay for GIA report in the case the grades will be lower than he presented.Alternatively you could ask independent professional appraiser to check the stone and verify IGI gradings.