Millimetres to UK ring size converter
A millimetre measurement of inner circumference converts neatly to a UK letter, because the UK scale is defined in millimetres (1.25 mm per letter from 40 mm at size C). About 51.8 mm is a UK L½ and 54.4 mm is a UK N½. Enter your measurement below.
Quick answer
A mm 54.4 is N½ in UK (about 54.4 mm inner circumference). Use the converter for your exact size, or the chart below for the full range.
Between two sizes? Size up for a comfortable fit, see how to measure accurately.
mm → UK at a glance
- 46.7 mm = H½
- 49.3 mm = J½
- 51.8 mm = L½
- 54.4 mm = N½
- 56.9 mm = P½
- 59.5 mm = R½
- 62.0 mm = T½
- 64.6 mm = V½
mm to UK ring size chart
| mmCircumference | UKUK / AU | mmDiameter |
|---|---|---|
| 46.7 | H½ | 14.9 |
| 48.0 | I½ | 15.3 |
| 49.3 | J½ | 15.7 |
| 50.5 | K½ | 16.1 |
| 51.8 | L½ | 16.5 |
| 53.1 | M½ | 16.9 |
| 54.4 | N½ | 17.3 |
| 55.6 | O½ | 17.7 |
| 56.9 | P½ | 18.1 |
| 58.2 | Q½ | 18.5 |
| 59.5 | R½ | 18.9 |
| 60.7 | S½ | 19.3 |
| 62.0 | T½ | 19.7 |
| 63.3 | U½ | 20.1 |
| 64.6 | V½ | 20.5 |
| 65.8 | W½ | 21.0 |
| 67.1 | X½ | 21.4 |
Common questions
How do I convert a mm ring size to UK?
Enter your mm size in the converter above and read the UK result, or find your row in the chart below. Every value is calculated from the ring’s inner circumference, so it works in both directions.
What is a mm 54.4 in UK?
A mm 54.4 is N½ in UK. That ring has an inner circumference of about 54.4 mm.
Related conversions
Or see the full ring size chart.