How to measure your ring size at home
You don’t need a jeweller to get a reliable size. Here are three accurate methods, ranked best first, plus the small mistakes that throw measurements off.
- 1
Measure a ring that already fits (best)
Take a ring the person already wears on the correct finger. With a ruler, measure straight across the inside from edge to edge, in millimetres or inches, that is the inner diameter. Enter it into the converter (use the mm/in toggle) to get the size in every system.
- 2
No ring? Use string or paper
Wrap a thin strip of paper or a piece of string snugly around the base of the finger, mark where it overlaps, and lay it flat against a ruler. That length is the inner circumference, read it in millimetres or inches. Convert it directly.
- 3
Convert and double-check
Enter your measurement, in millimetres or inches, or a size you already know, into the converter to read US, UK, EU and Japan sizes. Measure two or three times and take the average. If you land between sizes, choose the larger one.
Worked example
Say you measure the inside of a ring that fits and it’s 17.3 mm, about 0.68 in, across (the diameter). Multiply by π to get the circumference: 17.3 × 3.1416 ≈ 54.4 mm (2.14 in). That’s a US 7, a UK N½, an EU 54 and a Japan 14. If instead your paper strip came out at 51.8 mm (2.04 in) around, that’s a US 6 / UK L½ / EU 52.
Only have an inch ruler? Enter the same number, just switch the converter’s unit toggle to in and it does the rest.
Common mistakes to avoid
- Measuring cold hands. Fingers can change up to half a size, measure warm.
- Pulling the string too tight. It should slide over the knuckle, not pinch.
- Forgetting the knuckle. The ring has to pass it; if your knuckle is much larger, size to somewhere between the knuckle and the base.
- Ignoring band width. Wide bands fit tighter, add a quarter to a half size.
Prefer to measure on your phone?
The on-screen sizer calibrates to your exact screen with a bank card, then reads a ring you lay on the display.
Open the on-screen sizer →Frequently asked questions
What is the most accurate way to measure ring size at home?
Measuring the inner diameter of a ring that already fits is the most accurate home method, because it avoids soft tissue squashing. Measure across the inside in millimetres or inches and convert. If you have no ring, the string/paper method is a good second best.
When should I measure my finger?
Measure at the end of the day when your hands are warm and at their largest. Fingers shrink in the cold and swell in heat, after salty food, and during exercise, so an average, warm-hand reading gives the best everyday fit.
How much bigger should a ring be for a wide band?
Wide or comfort-fit bands (about 6 mm or more) feel tighter, so it is common to go up a quarter to a half size. If you are between sizes, size up.
Can I measure ring size with a phone?
Yes. Our on-screen sizer calibrates your screen against a standard bank card, then lets you lay a ring on the display or compare true-to-size circles to your finger.