Ring sizing is the single most common reason an online jewellery order has to be sent back. Get it roughly right the first time and you save two weeks of postage. Here is the UK and European conversion table, plus the tricks that actually work.
The three systems in use in Europe
- UK — alphabetical (F, G, H … Z, then Z+).
- EU / Germany — numerical, based on inner circumference in millimetres divided by π and rounded.
- US — numerical (4, 4.5, 5 …) — common on imported listings.
Conversion table
| UK | EU | Inside diameter (mm) |
|---|---|---|
| F | 44 | 14.0 |
| G | 45 | 14.4 |
| H | 47 | 14.8 |
| I | 48 | 15.1 |
| J | 49 | 15.5 |
| K | 50 | 15.9 |
| L | 51.5 | 16.3 |
| M | 52.5 | 16.7 |
| N | 54 | 17.1 |
| O | 55 | 17.5 |
| P | 56.5 | 17.9 |
| Q | 57.5 | 18.3 |
| R | 59 | 18.6 |
| S | 60 | 19.0 |
| T | 61.5 | 19.4 |
How to measure at home without them noticing
Borrow a ring
If you can sneak one of their rings for a few hours, drop it into a jeweller's sizing stick — most high-street shops will do this for free. Alternatively, trace the inner circle on a piece of paper and measure the diameter.
Measure with string
Wrap a piece of floss or thin paper around the base of the finger, mark the overlap, and measure the length against a ruler. That gives you the circumference. Divide by π (3.14159) to get the diameter, then look it up in the table.
Timing matters
Fingers are smaller in the morning and larger in the afternoon. They also swell in warm weather and after coffee. Measure at the end of the day, at room temperature, when they are not cold. If you are between sizes, size up — a slightly loose ring can be worn with a sizing bead; a too-tight ring is uncomfortable immediately.
Resizing after the proposal
Most solitaire rings can be resized by roughly two UK sizes either way. Rings with stones all the way around the band (eternity bands) usually cannot be resized at all — get the size exactly right on those. If you are ordering online, ask whether the seller includes one free resize.