WITHIN · SIZES · Updated 9 October 2026
US ring size 12.5 in mm, UK, EU and Japanese sizes
Where a US 12.5 sits on Blue Nile's chart, in every system it prints, with the sizes either side.
- Main chart: Blue Nile, read 9 October 2026
- Read: 9 October 2026
US 12.5 and the sizes either side
Ring sizes in every system, unisex
| US and Canada | UK and Australia | Europe | Japan and Singapore | Inside diameter (mm) |
|---|---|---|---|---|
| 12 | X 1/2 | 67 | 25 | 21.4 |
| Y | 21.6 | |||
| 12.5 | Z | 68 | 26 | 21.8 |
| Z 1/2 | 69 | 22 | ||
| 13 | 70 | 27 | 22.2 |
- Japanese sizes differ a little from one jeweller to the next. Cartier's chart puts a US 6 at Japan 12, where Blue Nile puts it at Japan 11. This table follows Blue Nile.
Source: Blue Nile (bn-dam.services.r2net.com), read 9 October 2026.
How to check at home
Lay a ring that already fits on Blue Nile's printed sizer. The circle that just fills the inside of the ring gives the diameter: for a US 12.5 it is the 21.8 mm circle.
The sizes either side
Shop in your size
Every piece on within shows the size its boutique printed and how many are left in it.
More on sizing
The full chart
Sources
- Blue Nile: Ring sizes for the US and Canada, the UK and Australia, Europe and Japan by inside diameter, and how to size a ring you already own. bn-dam.services.r2net.com, read 9 October 2026.