US to UK Ring Size Converter
US ring sizes are numbers, UK sizes are letters. This page converts between the two instantly and shows the full chart so you can double-check by hand.
Quick answer
US 7 is UK N½. As a rule of thumb, each full US size is about two letters in the UK system.
Instant Converter
Change any field — the rest update automatically.
Inside circumference, mm
Inside
Inside
Inside
Inside
Matched inside diameter 17.30 mm · circumference 54.35 mm
Conversion table
| US | UK | Inside diameter | Circumference |
|---|---|---|---|
| 3 | F | 14.00 mm | 44.0 mm |
| 3.5 | G | 14.40 mm | 45.2 mm |
| 4 | H | 14.80 mm | 46.5 mm |
| 4.5 | I | 15.20 mm | 47.8 mm |
| 5 | J½ | 15.60 mm | 49.0 mm |
| 5.5 | K½ | 16.00 mm | 50.3 mm |
| 6 | L½ | 16.45 mm | 51.7 mm |
| 6.5 | M½ | 16.90 mm | 53.1 mm |
| 7 | N½ | 17.30 mm | 54.3 mm |
| 7.5 | O½ | 17.70 mm | 55.6 mm |
| 8 | P½ | 18.10 mm | 56.9 mm |
| 8.5 | Q½ | 18.50 mm | 58.1 mm |
| 9 | R½ | 19.00 mm | 59.7 mm |
| 9.5 | S½ | 19.40 mm | 60.9 mm |
| 10 | T½ | 19.80 mm | 62.2 mm |
| 10.5 | U½ | 20.20 mm | 63.5 mm |
| 11 | V½ | 20.60 mm | 64.7 mm |
| 11.5 | W½ | 21.00 mm | 66.0 mm |
| 12 | X½ | 21.40 mm | 67.2 mm |
| 12.5 | Z | 21.80 mm | 68.5 mm |
| 13 | Z+1 | 22.20 mm | 69.7 mm |
Why the two systems differ
Both scales measure the same thing — the inside diameter of the band — but they were standardised separately. The US scale starts at size 0 and counts up in steps of about 0.8 mm of diameter. The UK scale runs A to Z with half-letter steps of roughly 0.4 mm.
Because the steps are different sizes, some US sizes land between UK letters. Charts round to the nearest half letter, which is why you may see a size quoted slightly differently by two jewellers.
Popular US to UK conversions
- US 5 = UK J½ (15.6 mm)
- US 6 = UK L½ (16.45 mm)
- US 7 = UK N½ (17.3 mm)
- US 8 = UK P½ (18.1 mm)
- US 9 = UK R½ (19.0 mm)
- US 10 = UK T½ (19.8 mm)
Buying from a US shop in the UK
Order by the millimetre measurement wherever the shop allows it — it removes the rounding entirely. If you can only choose a US number, take your UK letter, convert it here, and if you fall between two US sizes choose the larger one.
Frequently asked questions
What is a US size 7 in UK sizes?
A US 7 is a UK N½, with an inside diameter of 17.3 mm and an inside circumference of about 54.3 mm.
What is UK size L in US sizes?
UK L sits just under a US 5¾. UK L½ is the exact match for a US 6.
Keep reading
For an expensive ring, confirm the size with a jeweller before ordering — see the ring size FAQs for resizing advice.