US 5.5 to UK ring size
US ring size 5.5 is UK K½ — 16.10 mm inner diameter (50.6 mm circumference).
Your size is US 5.5 (UK K½, EU 51).
Fit confidence Exact table match
Measurement confidence 70/100 · Medium Standard chart conversion; final fit still depends on band width and knuckle shape. Confirm with a printable or physical sizer before ordering an expensive ring.
- US
- 5.5
- UK
- K½
- EU / ISO
- 51
- Japan
- 10
- CH / IT / ES
- 11
- Ø mm
- 16.10
- Circ mm
- 50.6
| US | UK | EU | JP | CH | Ø mm | Circ mm |
|---|---|---|---|---|---|---|
| 3 | F½ | 44 | 4 | 4 | 14.07 | 44.2 |
| 3.5 | G½ | 45 | 5 | 5 | 14.48 | 45.5 |
| 4 | H½ | 47 | 7 | 7 | 14.88 | 46.8 |
| 4.5 | I½ | 48 | 8 | 8 | 15.29 | 48.0 |
| 5 | J½ | 49 | 9 | 9 | 15.70 | 49.3 |
| 5.5 | K½ | 51 | 10 | 11 | 16.10 | 50.6 |
| 6 | L½ | 52 | 12 | 12 | 16.51 | 51.9 |
| 6.5 | M½ | 53 | 13 | 13 | 16.92 | 53.1 |
| 7 | N½ | 54 | 14 | 14 | 17.32 | 54.4 |
| 7.5 | O½ | 56 | 15 | 16 | 17.73 | 55.7 |
| 8 | P½ | 57 | 16 | 17 | 18.14 | 57.0 |
| 8.5 | Q½ | 58 | 17 | 18 | 18.54 | 58.3 |
| 9 | R½ | 60 | 18 | 20 | 18.95 | 59.5 |
| 9.5 | S½ | 61 | 19 | 21 | 19.35 | 60.8 |
| 10 | T½ | 62 | 20 | 22 | 19.76 | 62.1 |
| 10.5 | U½ | 63 | 22 | 23 | 20.17 | 63.4 |
| 11 | V½ | 65 | 23 | 25 | 20.57 | 64.6 |
| 11.5 | W½ | 66 | 24 | 26 | 20.98 | 65.9 |
| 12 | Y | 67 | 25 | 27 | 21.39 | 67.2 |
| 12.5 | Z | 68 | 26 | 28 | 21.79 | 68.5 |
| 13 | Z½ | 70 | 27 | 30 | 22.20 | 69.7 |
Nearby sizes
| US | UK | Ø mm |
|---|---|---|
| 5 | J½ | 15.70 |
| 6 | L½ | 16.51 |
Frequently asked questions
What is US 5.5 in UK ring size?
US ring size 5.5 is UK K½ (inner diameter 16.10 mm, circumference 50.6 mm).
Is US 5.5 the same as UK K½?
Yes — a US size 5.5 ring equals UK K½. They are different scales for the same physical size (16.10 mm inner diameter).
Explore
Ring Size Conversions — All Systems & Sizes · Size 5.5 · See the full international ring size chart