Quick answer: Tiffany & Co. lists ring sizes on the standard US scale, in half-size steps from 3 to 13, alongside the inside circumference in millimetres. Tiffany’s US 6 is 51.9 mm around, US 7 is 54.4 mm and US 8 is 57.0 mm. If you already know your US size, you do not need to convert anything.
How Tiffany ring sizes work
Tiffany’s size guide uses U.S. ring sizes shown with the inside circumference in millimetres, and its chart runs in half sizes (3, 3.5, 4 and so on up to 13). The circumference figures match the US scale on our own US ring size chart, so a US size from any other US-sized brand maps straight across.
Tiffany ring size chart (US 3–13)
The US size and circumference are from Tiffany’s size guide. The diameter (circumference divided by π) and the nearest whole EU/ISO size are calculated by us.
| Tiffany (US) size | Inside circumference | Inside diameter | Nearest EU size |
|---|---|---|---|
| 3 | 44.2 mm | 14.1 mm | EU 44 |
| 3.5 | 45.5 mm | 14.5 mm | EU 46 |
| 4 | 46.8 mm | 14.9 mm | EU 47 |
| 4.5 | 48.0 mm | 15.3 mm | EU 48 |
| 5 | 49.3 mm | 15.7 mm | EU 49 |
| 5.5 | 50.6 mm | 16.1 mm | EU 51 |
| 6 | 51.9 mm | 16.5 mm | EU 52 |
| 6.5 | 53.1 mm | 16.9 mm | EU 53 |
| 7 | 54.4 mm | 17.3 mm | EU 54 |
| 7.5 | 55.7 mm | 17.7 mm | EU 56 |
| 8 | 57.0 mm | 18.1 mm | EU 57 |
| 8.5 | 58.3 mm | 18.6 mm | EU 58 |
| 9 | 59.5 mm | 18.9 mm | EU 60 |
| 9.5 | 60.8 mm | 19.4 mm | EU 61 |
| 10 | 62.1 mm | 19.8 mm | EU 62 |
| 10.5 | 63.4 mm | 20.2 mm | EU 63 |
| 11 | 64.6 mm | 20.6 mm | EU 65 |
| 11.5 | 65.9 mm | 21.0 mm | EU 66 |
| 12 | 67.2 mm | 21.4 mm | EU 67 |
| 12.5 | 68.5 mm | 21.8 mm | EU 68 |
| 13 | 69.7 mm | 22.2 mm | EU 70 |
For UK letters, Japan and other systems, use the world ring size chart. To convert a European number, see European ring size to US.
Choosing between two sizes
Tiffany’s own guidance is that if you fall between sizes you should choose the larger one, since a ring is easier to make smaller than larger. That matches common jeweler advice, with one caution: a very loose ring can slide off, so do not round up by more than a half size without testing.
How to find your Tiffany size
- Measure the finger the ring will go on, using a string or paper strip, or a printable ring sizer.
- Match the inside circumference in mm to the chart above, or use the diameter if you measure a ring.
- Wide bands and stacked rings need a little extra room; see sizing for wide bands and the ring stacking sizing guide.
- Measure later in the day, when fingers are warm, and repeat a couple of times.
If you are buying an engagement ring, see our engagement ring sizing guide.
Frequently asked questions
What size system does Tiffany use?
The standard US ring size scale, with half sizes, shown with the inside circumference in mm.
What is Tiffany ring size 6 in mm?
An inside circumference of 51.9 mm, which is about 16.5 mm across.
What is Tiffany ring size 7 in mm?
54.4 mm inside circumference, about 17.3 mm across.
Does Tiffany offer quarter sizes?
Its size chart lists half sizes. Ask a Tiffany store about options if you are between sizes.
Is a Tiffany size the same as a Cartier size?
No. Tiffany uses US sizes, while Cartier uses European-style circumference numbers. See our Cartier ring size chart.
Should I size up if I am between sizes?
Tiffany’s guidance is to choose the larger size.
