In France, a ring's size corresponds to the inner circumference of the band, expressed in millimetres. A size 52, for example, means a 52 mm inner circumference. Here is how to determine the right size accurately, at home.
Method 1: measure an existing ring
This is the most reliable method, ideal for a surprise. Take a ring that already fits the right finger, measure its inner diameter in millimetres with a ruler, then multiply by 3.14 to get the circumference — that is the French size. For example, a 16.5 mm diameter gives a size 52.
Method 2: measure the finger with a strip
Wrap a piece of string or a thin strip of paper around the base of the finger, mark where it meets, then measure the length in millimetres with a ruler. This length corresponds directly to your French size. Make sure the strip slides over the knuckle without pinching.
Our tips for an accurate measurement
- Measure at the end of the day, when fingers are slightly larger.
- Avoid measuring in cold weather: fingers shrink.
- The ring should pass the knuckle without forcing, but not slip off on its own.
- Repeat the measurement two or three times to confirm.
Giving a surprise ring
If the ring is a surprise, discreetly borrow one they wear on the left or right ring finger, or enlist a trusted friend. When in doubt, remember that resizing is almost always possible afterwards: better a ring that is slightly too large than one that will not go on at all.
Once you know the size, all that remains is to choose the stone and the metal. Our guide to choosing an engagement ring helps you compose the whole piece, and our advisors are on hand for any question about resizing.