A ring half a size too large spins round. Half a size too small and it ends up in a drawer within a week. Measuring is not hard, but a few things often go wrong.
What the number means
In most of Europe the ring size is the inner circumference in millimetres. Size 54 is a ring with an inner circumference of 54 mm. Sometimes the inner diameter is given instead: the circumference divided by 3.14. Size 54 therefore has an inner diameter of about 17.2 mm.
The United Kingdom uses letters and the United States uses numbers on a scale of its own. If you order from a goldsmith abroad, give the circumference in millimetres. Every goldsmith understands that.
Measuring at home
With a ring that fits. Lay a ring that fits the same finger well on a ruler and measure the inside at its widest point, from edge to edge. Multiply by 3.14 and you have the circumference.
With a strip of paper. Wrap a narrow strip of paper around the finger, mark where it overlaps and measure the length. This is less accurate, because paper does not tell you whether the ring will pass the knuckle. Use it as an estimate.
At a goldsmith. Trying on sizing rings is the most accurate way. It takes two minutes and usually costs nothing.
Mistakes people often make
- Measuring with cold hands. Fingers are slimmer in the morning and in the cold. Measure at the end of the day, at room temperature.
- Forgetting the knuckle. The ring has to pass the knuckle. If the knuckle is wider than the base of the finger, choose the size that only just slides over it.
- Sizing a wide ring like a narrow one. A wide ring fits tighter. For a band from about 6 mm wide, expect to go up half a size to a full size, and try on a wide sizing ring.
- The wrong hand. The fingers of the hand you write with are often slightly thicker.
Finding out the size in secret
- Borrow a ring that is worn on the same finger and measure the inner diameter, or press it into a bar of soap.
- Slide the ring onto your own finger and mark how far it goes. A goldsmith can measure that point.
- Ask a friend or relative. They often know, or can find out without raising suspicion.
If you are between two sizes, choose the larger. Making a ring smaller is easier than making it larger.
Can a ring be resized later?
Usually, by a size or two. There are exceptions: a ring set with stones all the way round, a ring with a continuous pattern or engraving, and some materials such as titanium. Ask about it before the design is final.
When a ring is made for you, the size is part of the conversation with the goldsmith. Describe your ring and mention what you already know, even if that is only "her grandmother’s ring fits her middle finger". For ideas, see the engagement rings and wedding rings by independent goldsmiths.