Rings (and to less extent, bracelets) are the only jewelry pieces which need exact ring sizing.
Sizes can be measured in different ways. There are Australian/British, US, General European (German), French and Japanese ring sizing scales.
I find the General European ring sizing scale most logical because it is based on the inside diameter of the ring in millimeters. Using the following formula: L = D+MT (mm) x 3,14, where L = length, D = inside diameter in mm, MT = material thickness in mm, it is easy for a jewelry maker to connect the size to the lentgh of the piece to be used as a ring shank. But mathematics works great when there are no unknowns. And the first ‘unknown’ is the diameter of the customer’s finger.
Happily there are many ring sizing guidelines on the internet which help the customer to find his or her ring size. For instance, this one:
- Wrap a piece of string or a strip of paper around your finger.
- Mark the point where the two ends meet.
- Measure the string or paper against a ruler to get the circumference of your finger.
- Note this number and/or divide it by 3.14 to get the diameter of your finger.
But what if a customer DOES NOT know the size of the prospective ring wearer and wants the ring to make a surprise?
The ring buyer can use the following tips to know someone else’s size – only approximate
#1 tip is to obtain and measure a ring the wearer already owns.
# 2 tip is to let her/him try a ring of your own (“oh look, you should try this one”)
Some people advise to play a guessing or a betting game (“bet your finger will get through THIS keyring?”)
One can also try to guess the size based on the general size of the person related to the general population. Is she on the small or on the large side? For instance, in the Netherlands size 18 is the average women’s ring size. But in other countries it may differ.
Of course this kind of measurement will always lack precision. But is this a major problem? Actually not, because there are many fingers to wear rings on, not just the ringfinger. Some ring styles look best on other fingers. Delicate rings, for example, look lovely and demure on your ring finger. Cocktail rings may show better on your middle finger or pointer finger. Large bands can be worn on the thumb for an edgier look; thumb rings are perfect for your men’s jewelry collection. Pinky rings are also available. Pinky rings are typically petite and feminine, though many styles are offered to suit a variety of tastes.
By the way, did you know that our fingers can change their thicknes depending on many factors? Not only gaining or losing weight, but also gaining or losing water could be of influence.
Upsizing and downsizing
The last piece of advise: for the (amateur) jewelry maker who does not have expensive ring sizing equipment.
Upsizing by 1 US or 1/2 European size is in most cases possible without dismantling the ring.
It is not recommended that a ring be adjusted by more than one or two full (US) sizes. The ring shank has to be thick and solid enough for this. You just put a ring on a mandrel and start tapping it all around the circumference of the ring with a rawhide mallet, which has a metal head covered in rawhide. This softens the blow when it comes in contact with metal, making it ideal for working on jewelry. If you want more size increase (and a hammered look), use a hammer.
Downsizing is much more tricky. In many cases the ring has to be dismantled, the stone removed etc. Sometimes, when the ring has no heat sensitive stone, you can cut out a segment on the side of the ring opposite to the top and re-solder the ends. For this purpose it is recommended to solder the ring ends first and to attach the top on the side opposite to the solder joint (see picture).