Calibrated Gemstone Education

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What Does Calibrated Mean when it comes to Gemstones
Why is it important to know

Gemstone Calibration Education for Jewelry. Gemstone Sizes in Calibrated measurements. Loose Gemstones can fall out; tight gems can ruin settings and prongs. Buy Loose Calibrated Gems that fit the Settings. All Loose Stones fall between calibrated ranges, and many settings will call for certain stone measurements. Calibration sizes takes care of this for you. One should keep in mind that not all settings will be available or in stock for various sizes of gemstones. In such cases, it may be necessary to actually make a “custom made” setting for your item. This may be particularly true when it is a larger cut stone or a “fancy” cut stone that is not cut to what we refer to as normal sizes.

More information can be found below when it comes to Calibrated gemstone sizes.


Custom Made Jewelry and Settings from Not Just Stones

Not Just Stones can assist you in creating custom made and fancy settings. Send us an email at, or look in our Custom Made Settings and Custom Made Jewelry links under our Special orders section.


More information about Calibrated Stones sizes from Not Just Stones

When we mention the term "Calibrated,” it does, in rough translation, mean "exact." However, for the sake of argument, we will say “very close to it.” So close that you cannot literally tell the difference with the eye naked.

Calibrated stones are typically within .20 mm of the calibrated size in each direction (and that can “stretch” to .30 which is generally the case with most calibrated stones). The difference in the “stretch” if you will, can be the thickness that is in question; though the “stretch” can be so minute in either direction (.20 - .30 for example) that one does not have to worry anyway. In any case, you literally cannot tell the difference with the eye naked.

In terms of preciseness and size for the differential noted above when it comes to stones at the calibration level, to use an example by way of Metrics, a differential of .20 -.30 would mean that there would be a possible differential of between .0078 (.20) - .0118 (.30) (decimal) inches which is less than 1/64 of an inch; and as it stands, the next place directly below this 1/64th mark would be of course our upper scale mark (.30 (.0118 (decimal))) differential; if the differential were to be extended to that next lower level of .30.

In metric conversion description, 1/64th is precisely equal to .0156 (decimal) or .3969 mm if you want to be exact. If we round two places, the 1/64th would be directly proportional to the equivalent of the next higher metric number of .40 mm. (0.3969 – the hundredth place 9 (0.39)) rounded up to 4, and dropping both the 6 in the thousandth place (0.396), and the 9 in the millionth place (0.3969). Again, in direct translation, this rounded number is precisely 1 place above our highest potential differential of .30, which we have already outlined previously above.

Examples of Calibrated Stone Uses
Based on Stones that Are Round Shaped

Setting Calls for the Following

Size you need, minimum.

Size you need, maximum.


0.70 mm

1.30 mm


1.70 mm

2.30 mm


2.70 mm

3.30 mm


3.70 mm

4.30 mm


4.70 mm

5.30 mm


5.70 mm

6.30 mm


6.70 mm

7.30 mm


7.70 mm

8.30 mm


8.70 mm

9.30 mm


9.70 mm

10.30 mm


  1. Even though the minimum and maximum sizes are shown, this is somewhat misleading as shown below as it does not necessarily always hold true. To get the best possible fit for the setting though, these are the suggested sizes that should be used when it comes to round cut stones.

  2. If the setting for example calls for a 7mm stone and your stone measures more than 7.30mm, the stone may still work; however, it may end up being a tight fit which may not be good for the facets. In such case, though you may still be able to use the stone, to avoid potential problems, you may want to go with a different size that falls within the calibrated ranges.

  3. If the setting for example calls for a 7mm stone and your stone measures less than 6.70mm, the stone may still work; however, it can end up being too loose in the setting and you might end up ruining the setting trying to make it fit right or even eventually lose the stone because it does not fit right. Though you may be able to still use the stone, in such case, to avoid potential problems, you may want to go with a different size that falls within the calibrated ranges.


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