Ring Size Converter
Ring sizing is unusual because the systems are not related by a formula. A US 7, a UK N and a European 54 are three names for roughly the same finger, and the only reliable bridge between them is the inside diameter of the ring in millimetres. This converter is built on that measurement, which is what you should take from the wearer.
Convert a measurement
Enter your own figure, pick the units on each side, and the result is worked out as you go. Nothing is stored.
All units at once
The same quantity written every way this page knows, so you do not have to convert twice.
Nothing entered yet, so the table below starts from the closest row of the chart.
| Unit | Value |
|---|---|
| Inside diameter (mm) Starting value | 14.1 |
| US size | 3 |
| UK / Australian letter | F |
| European size | 44 |
| Inside circumference (mm) | 44.2 |
Full size chart
Every size in the standard, printed in full. Read across a row to translate one size into the other systems, or find the measurement you took and take the names beside it.
| Inside diameter (mm) | Inside circumference (mm) | US size | UK / Australian letter | European size |
|---|---|---|---|---|
| 14.1 | 44.2 | 3 | F | 44 |
| 14.5 | 45.5 | 3.5 | G | 45 |
| 14.9 | 46.8 | 4 | H | 47 |
| 15.3 | 48 | 4.5 | I | 48 |
| 15.7 | 49.3 | 5 | J | 49 |
| 16.1 | 50.6 | 5.5 | K | 50 |
| 16.5 | 51.9 | 6 | L | 52 |
| 16.9 | 53.1 | 6.5 | M | 53 |
| 17.3 | 54.4 | 7 | N | 54 |
| 17.7 | 55.7 | 7.5 | O | 55 |
| 18.1 | 57 | 8 | P | 57 |
| 18.5 | 58.3 | 8.5 | Q | 58 |
| 19 | 59.5 | 9 | R | 59 |
| 19.4 | 60.8 | 9.5 | S | 60 |
| 19.8 | 62.1 | 10 | T | 62 |
| 20.2 | 63.4 | 10.5 | U | 63 |
| 20.6 | 64.6 | 11 | V | 64 |
| 21 | 65.9 | 11.5 | W | 66 |
| 21.4 | 67.2 | 12 | X | 67 |
| 21.8 | 68.5 | 12.5 | Y | 68 |
| 22.2 | 69.7 | 13 | Z | 70 |
What this assumes
- Measure the inside diameter of a ring that already fits, in millimetres, and use that as your starting point. Paper strips and string stretch, and they are the reason most home ring measurements come out wrong.
- Finger size changes with temperature and time of day, sometimes by half a size. Measure at the end of the day when your hands are warmest, and take the measurement twice.
- A wide band fits tighter than a narrow one at the same diameter. Allow about a quarter size up for a band wider than about 6 millimetres.
- This chart is a guide for sizing jewellery. It is not a substitute for a proper fitting by a jeweller if the ring matters.
Every figure on this page is worked out from millimetres of inside diameter, and the page states the factor rather than hiding it.
Questions people ask
What is a US size 7 in UK sizes?
A US 7 is a UK N and a European 54, with an inside diameter of about 17.3 millimetres. If you are working from a measurement rather than a size, measure the inside diameter and read across the chart.
How do I measure my ring size at home?
Take a ring that already fits and measure its inside diameter with a ruler or callipers, in millimetres. Compare that to the chart above. Measuring your finger with a strip of paper is much less reliable because the paper stretches and the finger compresses.
Why does my ring size differ between shops?
Because the standards are not perfectly aligned, and because band width and profile change the fit. Two rings with the same inside diameter can feel different if one is a wide flat band and the other is a thin court shape.
Does ring size change with weight?
Yes. Weight change, pregnancy, and even salty food can move a finger by half a size or more. If a ring is being made to order, measure at a stable time and mention any recent change to the jeweller.