Guide
How to find your ring size at home.
A smart ring is wider than most jewellery and stays on your finger all day, so the fit matters more. You can measure at home with a strip of paper, or with a ring that already fits.
Two ways to measure
With a strip of paper
- Cut a thin strip of paper, about 5 mm wide.
- Wrap it round the base of the finger you will wear the ring on: snug, not tight.
- Mark where the paper overlaps, lay it flat and measure the length in millimetres. That is your circumference.
- Check the knuckle: the ring has to pass over it. If your knuckle is much wider, measure there too and choose between the two.
With a ring that already fits
Measure the inside diameter of a ring that fits the same finger, edge to edge across the middle, in millimetres, and find the nearest row below, or let the ring size calculator do it.
Size table
| US size | Inside diameter | Inside circumference (EU size) | UK size, about |
|---|---|---|---|
| 6 | 16.5 mm | 51.9 mm | L½ |
| 7 | 17.3 mm | 54.4 mm | N½ |
| 8 | 18.1 mm | 57.0 mm | P½ |
| 9 | 19.0 mm | 59.5 mm | R½ |
| 10 | 19.8 mm | 62.1 mm | T½ |
| 11 | 20.6 mm | 64.6 mm | V½ |
| 12 | 21.4 mm | 67.2 mm | X½ |
| 13 | 22.2 mm | 69.7 mm | Z+1 |
US sizes follow the common rule of 11.63 mm plus 0.8128 mm per size for the inside diameter. EU sizes (ISO 8653) are the inside circumference in millimetres. Charts differ a little between makers, so treat the UK letters as a guide.
Why smart rings fit differently
- They are wider. A wide band feels tighter than a thin one of the same size. If you are between two sizes, the larger one is usually more comfortable.
- They have a top. A ring with a screen or a button has to sit the right way up, so it should be snug enough not to spin.
- Fingers change during the day. Measure in the afternoon or evening, when fingers are a little larger, and not when your hands are cold.
- Choose the finger first. For a ring you press with your thumb, the index or middle finger is the natural place. Measure the one you choose.
Lychnos Ring sizes
Lychnos Ring is planned in US sizes 6 to 13. If you are not sure of yours, you will be able to choose “not sure yet” when pre-orders open. More about the ring in the overview.
Questions
Is my ring size the same on both hands?
Often not: the dominant hand is usually a little larger. Measure the finger and the hand you will wear the ring on.
How tight should a smart ring be?
Snug: it should not spin or slip over the knuckle easily, and it should not leave a deep mark when you take it off.