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Stone size for eternity ring


I wanted to give a go at the technique for setting stones in the same fashion that they are set for an eternity ring. I have a couple of questions.

  1. How much metal is typically allotted on each side to make the prongs
    2 how do you determine how many stones are needed to complete the ring. And/Or how to adjust the spacing of the stones to accommodate their size in relation to the ring size. If there is a mathematical formula that would be great.
  2. What are some other helpful tips? I’m using the bare essentials. Saw blade, ball and setting burs, files.
    Thanks in advance,


Hey Matt,
Having just failed at this, I was subsequently advised to leave 1mm on either side. As for number of stones, using PowerPoint, I laid out a circle a little smaller than my ring and divided it with a number of line segments.

Remember as you plan the seats for the stones, the effective circumference at the depth of girdles is smaller than the outer circumference of the ring, so leave adequate space.

Hope this helps, and good luck.


Mathew, to get this right is not all that hard but to get is wrong is easy.
To keep the instructions short. From your photo draw another circle outside the eighteen stones and multiply that be “pi”, giving you the number of stones and gaps that you can envisage in the eternity band.
Draw another circle inside your stones that is your finger diameter but leave a clearance gap for an extra deep stone. To start thinking of your stones as spheres is a good start. If by colour your stones are garnets they often have thick girdles, or 100 % height by width.
With diamonds (rounds) are sixty percent of the depth but Princess cut are seventy percent in depth. You cannot change the math equation but it works in your favour to use it all the time.


Hi Matthew

CAD makes EZ work for layout. If you can supply me with stone size, ring size and height from ring rail to top of stone table I can lay out for you. I am assuming setting will have shared prongs?



I like the look of stones being girdle to girdle with what appears to be no space between the stones. The trick is to remember that when laying them out you need to have a little more space between the stones. As you cut the seats in metal or wax the stones sit lower than they did when just resting on the outside. As they go lower the circumfrence gets smaller. If the girdles actually touch each other you run the risk of them chipping each other while setting.


Thank you everyone for your input. A couple of things I want to address or clarify from different replies.
Alec, thanks for sharing. I’m assuming that the 1mm on either side would mean if my stones were 2mm I would need a shank that is 4mm wide, right? Are you also talking about 1mm for the space between the stones to insure there is enough space once the seat is cut in?
John, Thanks for adding on to the picture about the outer and inner circles. In regards to the 100% height by width compared to 60%. That would mean a 2mm wide stone with 100% would be 2mm high, from the girdle or table? And I would expect that at 60% the height would be 1.2mm?
Also, is there a typical diameter stone?