Carats to mm?

posted 1 year ago in Engagement
Post # 4
Member
133 posts
Blushing bee

It does depend on shape:

https://bnsec.bluenile.com/bnsecure/assets/chrome/pdf/diamond_carat_size_0810.pdf or https://www.fourmine.com/education/diamond-education/diamond-size-chart

Different shapes face up different sizes. For example, a round brilliant that’s 6.5mm would be about 1 ct, but a cushion or princess cut 6.5mm across would be about 1.5 ct. Unless they’re very familiar with diamonds, people are going to see the physical size rather than the equivalent carat weight, though…

Post # 5
Member
731 posts
Busy bee
  • Wedding: June 2019

My stone is a 6.5mm round Moissanite and it appears to be the size of a one carat diamond 🙂 Like someone else said above, I think the range you’re seeing is due to shape. 6.5mm should be 1ct if you’re going for a round stone 🙂 

Post # 7
Member
2674 posts
Sugar bee

mel2 :  If it helps, my 2.2 ct cushion is 6.98 mm x 7.68 mm.  

Post # 8
Member
1887 posts
Buzzing bee
  • Wedding: October 2019

 Cushions are known for facing up small… you have to have a bigger weight diamond to have similar finger overage of a smaller weight in different cut.

I don’t know that you can tell what it’ll look like until it is on your finger.  Absent that,  I’d trust the expert. 

Post # 9
Member
133 posts
Blushing bee

mel2 :  search large collections of diamonds (Blue Nile, James Allen) for cushion cuts to see the actual size range for diamonds. The charts I gave were for “best” proportions, but stones can be cut deeper, shallower, etc. giving rise to some variation in carats to size. (I’d be very surprised by a 1-1.5 ct range, though.)

But again, I would probably focus more on the physical size and how it looks to you, rather than what equivalent carat weight it has.

Post # 10
Member
2674 posts
Sugar bee

And keep in mind that a square cushion will face up smaller.  So it might technically be 1.5 ct equivalent, but it will look closer to a 1 ct.

Post # 11
Member
113 posts
Blushing bee

https://moissaniteco.com/download/moissanite-comparison.pdf

This is the most helpful conversion chart I found when trying to decide on size for moissanite. I printed it out and sat a quarter on top of the paper to ensure it was an accurate representation, and I actually cut out the gems and sat them on top of my finger to picture what it would look like.  It won’t give you a sense of what the depth will be, but it is helpful in trying to picture finger coverage. 

Post # 12
Member
971 posts
Busy bee
  • Wedding: October 2015

Don’t get caught up in the carat weight

Post # 13
Member
2674 posts
Sugar bee

I also recommend going and trying on certain sizes.  I tried on a 1.5 ct stone and it seems so tiny on my hand.  2.2 ct looks perfect without looking over the top.

Post # 14
Member
540 posts
Busy bee
  • Wedding: October 2020 - New York, New York

I’m not a jeweler but I ran into this when I was trying to pick out my asscher from Charles and Colvard. An 8mm round diamond is usually 2 carats, while 8mm diamond asscher is typically 3 carats because asschers carry more weight in the pavilion or the lower part of the stone. I was confused why the 8mm Charles & Colvard asscher is approximately 2 carats (when most 8mm asschers are 3 carats), but it’s because it has less weight in the pavilion (and as a result, it isn’t as high set on your finger). 

Image result for parts of a stone

A 6.5×6.5 stone that’s 1.5 carats will just have more weight in the lower part of the stone than a 6.5×6.5 stone that’s 1 carat. The 1.5 carat stone would sit a little higher, but the difference would be minor since milimeters are so small. 

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