Ring size guide: the conversion table in mm

Updated: 29 September 2026 | Maison de l'Amour

1. What “size 54” actually means

Several systems exist around the world, and that is where the confusion starts. In France and across much of Europe, the measurement is the finger circumference: the size matches the inside circumference of the ring, in millimetres.

Jewellers sometimes speak in diameter rather than circumference. One follows from the other, since a circle's circumference equals its diameter times 3.14. That is all there is to remember.

2. The ring size table

Here is the full conversion, from size 47 to size 70.

Size (finger circumference)	Inside diameter
47	15.0 mm
48	15.3 mm
49	15.6 mm
50	15.9 mm
51	16.2 mm
52	16.6 mm
53	16.9 mm
54	17.2 mm
55	17.5 mm
56	17.8 mm
57	18.1 mm
58	18.5 mm
59	18.8 mm
60	19.1 mm
61	19.4 mm
62	19.7 mm
63	20.1 mm
64	20.4 mm
65	20.7 mm
66	21.0 mm
67	21.3 mm
68	21.6 mm
69	22.0 mm
70	22.3 mm

The sizes in bold are the most common among women. 54 is by far the most requested.

3. Find your size in two minutes

No ring sizer needed. Wrap a strip of paper or a piece of thread around the base of your finger, mark where it overlaps, unroll it and measure the length with a ruler. That length in millimetres is your size: 54 mm around the finger means a size 54.

The detailed method, with the mistakes to avoid, is in our article on measuring your ring size at home without a ring sizer. For bracelets, necklaces and earrings, every measurement is gathered on our size guide.

4. Our rings are adjustable: what that changes

This is the most important point of this guide. All our rings are adjustable: the band is open and tightens or widens slightly with your fingers. So you do not need to know your size to the millimetre, and that is what makes them a risk-free gift.

One useful detail all the same: the range covered is not the same on every model. Most go from 52 to 60 or from 52 to 62, but some pieces cover a shorter range. The exact range is shown on each product page, in the description. If you are below 52 or above 62, check it before ordering.

A few models with a wide range: the CAPUCINE (18 €), the ESRA (18 €) and the DAHLIA (18 €) all cover 52 to 62.

Why an open band, and why it does not break: it is explained in three reasons to choose an adjustable ring.

5. The three mistakes that skew the measurement

• Measuring in the morning or in the cold. Fingers are at their smallest. Measure at the end of the day, at normal temperature.
• Pulling the strip tight. The strip should rest, not stretch. A tight thread costs you a whole size.
• Forgetting that fingers change. Heat, sport, late pregnancy: finger circumference varies by one or two sizes over a year. That is exactly what an adjustable ring absorbs.

Frequently asked questions

What is the most common ring size for women?

Size 54, which is 17.2 mm inside diameter. Sizes 52 to 56 cover the vast majority of women's hands.

How do you convert a ring size into millimetres?

In France the size is the finger circumference in millimetres, so there is nothing to convert. For the diameter, divide by 3.14: a size 56 gives 17.8 mm.

Do I need to know my size to order from you?

No. All our rings are adjustable. Simply check the range shown on the product page if you are below 52 or above 62.

How do you measure someone's size without them knowing?

Borrow a ring they already wear on the right finger and measure its inside diameter with a ruler, then read it off the table above. For a gift, an adjustable ring remains the safest option.

Does an adjustable ring lose its shape over time?

It is designed to open slightly, not to be bent repeatedly. Adjust it once to your finger, then slide it on normally. In stainless steel it keeps its shape and does not tarnish.