UK, Ireland and Australia ring sizes
UK, Irish and Australian ring sizes are letters: each letter adds 1.25 mm of circumference and C is 40 mm, so A is 37.5 mm and N½ is 54.4 mm round, the same as US 7.
Defined by a published standard.
Where it is used: United Kingdom, Ireland, Australia, New Zealand
UK, Ireland and Australia size table
| UK, Ireland and Australia size | Inside Ø mm | Circumference mm | Nearest US | Nearest UK | Nearest ISO |
|---|---|---|---|---|---|
| F½ | 14.1 | 44.4 | ≈ 3 | F½ | ≈ 44 |
| G | 14.3 | 45.0 | ≈ 3.25 | G | 45 |
| G½ | 14.5 | 45.6 | ≈ 3.5 | G½ | ≈ 46 |
| H | 14.7 | 46.3 | 3.75 | H | ≈ 46 |
| H½ | 14.9 | 46.9 | 4 | H½ | 47 |
| I | 15.1 | 47.5 | 4.25 | I | ≈ 48 |
| I½ | 15.3 | 48.1 | 4.5 | I½ | 48 |
| J | 15.5 | 48.8 | 4.75 | J | ≈ 49 |
| J½ | 15.7 | 49.4 | 5 | J½ | ≈ 49 |
| K | 15.9 | 50.0 | 5.25 | K | 50 |
| K½ | 16.1 | 50.6 | 5.5 | K½ | ≈ 51 |
| L | 16.3 | 51.3 | 5.75 | L | ≈ 51 |
| L½ | 16.5 | 51.9 | 6 | L½ | 52 |
| M | 16.7 | 52.5 | 6.25 | M | ≈ 53 |
| M½ | 16.9 | 53.1 | 6.5 | M½ | 53 |
| N | 17.1 | 53.8 | 6.75 | N | ≈ 54 |
| N½ | 17.3 | 54.4 | 7 | N½ | ≈ 54 |
| O | 17.5 | 55.0 | 7.25 | O | 55 |
| O½ | 17.7 | 55.6 | 7.5 | O½ | ≈ 56 |
| P | 17.9 | 56.3 | 7.75 | P | ≈ 56 |
| P½ | 18.1 | 56.9 | 8 | P½ | 57 |
| Q | 18.3 | 57.5 | 8.25 | Q | ≈ 58 |
| Q½ | 18.5 | 58.1 | 8.5 | Q½ | 58 |
| R | 18.7 | 58.8 | 8.75 | R | ≈ 59 |
| R½ | 18.9 | 59.4 | 9 | R½ | ≈ 59 |
| S | 19.1 | 60.0 | ≈ 9.25 | S | 60 |
| S½ | 19.3 | 60.6 | ≈ 9.5 | S½ | ≈ 61 |
| T | 19.5 | 61.3 | ≈ 9.75 | T | ≈ 61 |
| T½ | 19.7 | 61.9 | ≈ 10 | T½ | 62 |
| U | 19.9 | 62.5 | ≈ 10.25 | U | ≈ 63 |
| U½ | 20.1 | 63.1 | ≈ 10.5 | U½ | 63 |
| V | 20.3 | 63.8 | ≈ 10.75 | V | ≈ 64 |
| V½ | 20.5 | 64.4 | ≈ 11 | V½ | ≈ 64 |
| W | 20.7 | 65.0 | ≈ 11.25 | W | 65 |
| W½ | 20.9 | 65.6 | ≈ 11.5 | W½ | ≈ 66 |
| X | 21.1 | 66.3 | ≈ 11.75 | X | ≈ 66 |
| X½ | 21.3 | 66.9 | ≈ 12 | X½ | 67 |
| Y | 21.5 | 67.5 | ≈ 12.25 | Y | ≈ 68 |
| Y½ | 21.7 | 68.1 | ≈ 12.25 | Y½ | 68 |
| Z | 21.9 | 68.8 | ≈ 12.5 | Z | ≈ 69 |
| Z½ | 22.1 | 69.4 | ≈ 12.75 | Z½ | ≈ 69 |
| Z+1 | 22.3 | 70.0 | ≈ 13 | Z+1 | 70 |
| Z+1½ | 22.5 | 70.6 | ≈ 13.25 | Z+1½ | ≈ 71 |
| Z+2 | 22.7 | 71.3 | ≈ 13.5 | Z+2 | ≈ 71 |
| Z+2½ | 22.9 | 71.9 | ≈ 13.75 | Z+2½ | 72 |
About UK, Ireland and Australia sizes
The UK, Ireland and Australia system uses letter sizes in GB, IE, AU and NZ. A US 7 corresponds to UK N½, which has a circumference of 54.4 mm. The letter shows a place on a shared scale, while the half letter marks a smaller step between whole letters.
The scale comes from British Standard BS 6820:1987 and is based on the international ring size standard. Other systems may use numbers, so the same ring can have different labels: UK N½ is ISO 54. One chart trap is that some brands place UK letters about 0.6 mm off this scale, so charts may disagree for the same ring.
Use the table to compare the UK letter with the equivalent sizes in other systems. Before buying, check the shop’s own chart and measure a ring that fits the intended finger. The RingSteps converter can help compare labels, and the printable sizer can help check size at home.
Sources
- Ring size (Wikipedia) Checked November 10, 2026