Cartier Ring Size Chart: Cartier to US and UK Sizes

Cartier sizes its rings in the French system, where the size is the ring's inside circumference in millimeters. Here's how each size converts to US and UK sizes, and how to find yours.

Updated

A ring with its inside circumference marked as 52 mm, labeled French size 52, which is about US size 6 and UK size L½

Cartier sizes its rings in the French system: the size number is the inside circumference of the ring in millimeters. A Cartier size 52 is 52 mm around the inside, or 16.6 mm across. It’s the same as the European (ISO 8653) system, so the conversion to US and UK sizes is straightforward.

Accurate Online Ruler isn’t affiliated with Cartier. The US and UK equivalents below are calculated from the standard size definitions and rounded to the nearest quarter size. For an expensive purchase, confirm with Cartier’s own sizing guide or a boutique.

Cartier ring size chart

Cartier (French) size Inside diameter US size (approx.) UK size (approx.)
46 14.6 mm 3¾ G½
47 15.0 mm 4 H
48 15.3 mm 4½ I
49 15.6 mm 5 J½
50 15.9 mm 5¼ K
51 16.2 mm 5¾ L
52 16.6 mm 6 L½
53 16.9 mm 6½ M½
54 17.2 mm 6¾ N
55 17.5 mm 7¼ O
56 17.8 mm 7½ O½
57 18.1 mm 8 P½
58 18.5 mm 8½ Q¼
59 18.8 mm 8¾ R
60 19.1 mm 9¼ S
61 19.4 mm 9½ S½
62 19.7 mm 10 T½

To check a size for real, place a ring you own on the ring size finder and set it to the matching US size, for example US size 6 for a Cartier 52. It draws the ring at actual size on your screen.

How to find your Cartier size at home

  1. Measure around your finger. Wrap a thin strip of paper around the base of the finger, mark the overlap and measure it in millimeters. That number, rounded, is your Cartier size. The mm to ring size converter shows the US and UK sizes too.
  2. Or measure a ring that fits. Use the on-screen ring sizer after calibrating with a bank card, and read the EU size. It’s the same as the Cartier size.
  3. Or print a sizer. The printable ring sizer has a paper strip marked in millimeters, so the reading at the slit is your French size.

Tips before you order

  • Measure later in the day and at room temperature. Fingers are smaller when cold.
  • Check over the knuckle. If your knuckle is wide, choose a size that passes over it.
  • Between sizes? Go up. A slightly loose ring is easier to live with than one you can’t get on.
  • Wide bands fit tighter. Consider one size up for wide styles, and confirm with the boutique.

French sizes are also used by many other European jewelers, so this chart works for any ring sold in French or European sizes.

Frequently asked questions

What is Cartier size 52 in US sizes?

About a US size 6 (UK L½). Cartier uses French sizes, where 52 means an inside circumference of 52 mm, which is 16.6 mm across.

Are Cartier sizes the same as European sizes?

Yes. French ring sizes, which Cartier uses, are the same as the European ISO 8653 sizes: the inside circumference in millimeters. A Cartier 54 is the same size as a Pandora 54 or any other European 54.

How do I convert my US ring size to a Cartier size?

Find your US size in the chart and read the Cartier size next to it, or use the formula: circumference (mm) = 3.1416 × (11.63 + 0.8128 × US size). A US 7 is 3.1416 × 17.32 = 54.4 mm, so a Cartier 54.

Should I size up for a wide Cartier ring?

Wide bands touch more of your finger and feel tighter than thin ones, so many people go up one size for wide rings. Cartier's boutiques and its printable sizing guide can help confirm the size for a specific model before you buy.

More measuring guides