EU / ISO to UK / AU ring size
The short answer
By the formula, EU / ISO 57 is UK / AU P 1/2.
Inner circumference 57 mm. Ring sizes are defined by that one measurement, so this conversion is exact up to rounding: US sizes are rounded to the nearest quarter, UK letters to the nearest half.
| EU / ISO | UK / AU |
|---|---|
| 44 | F |
| 45 | G |
| 46 | H |
| 47 | H 1/2 |
| 48 | I 1/2 |
| 49 | J |
| 50 | K |
| 51 | L |
| 52 | L 1/2 |
| 53 | M 1/2 |
| 54 | N |
| 55 | O |
| 56 | P |
| 57 | P 1/2 |
| 58 | Q 1/2 |
| 59 | R |
| 60 | S |
| 61 | T |
| 62 | T 1/2 |
| 63 | U 1/2 |
| 64 | V |
| 65 | W |
| 66 | X |
| 67 | X 1/2 |
| 68 | Y 1/2 |
| 69 | Z |