Ring Size Converter
Convert ring sizes between US, UK/AU, EU, JP, KR and circumference/diameter (mm) instantly
π How to Measure Your Ring Size
𧡠String / Thread Method
- Wrap a piece of string or thread snugly around the base of your finger.
- Mark where the string overlaps with a pen.
- Lay the string flat and measure the length in millimeters.
- This is your circumference β use the converter above to find your size.
π Paper Strip Method
- Cut a thin strip of paper (about 10mm wide, 100mm long).
- Wrap it around the base of your finger β snug but comfortable.
- Mark where the paper overlaps.
- Measure the length from the edge to the mark in millimeters.
- Enter this circumference in the converter above.
π Existing Ring Method
- Place a ring that fits well on a ruler.
- Measure the inside diameter in millimeters.
- Enter this diameter in the converter above.
π‘οΈ Seasonal & Sizing Tips
βοΈ Fingers swell in warm weather. If you're between sizes, size up in summer.
βοΈ Fingers shrink in cold weather. A ring that fits in winter may be loose in summer.
π Measure in the evening when fingers are at their largest.
β Your dominant hand is typically slightly larger. Measure the specific finger you'll wear the ring on.
Measuring and Converting Ring Sizes Accurately
Different systems by country
- US: numbers with halves (6, 6.5, 7β¦)
- UK: letters (L, M, Nβ¦)
- EU/ISO 8653: the inner circumference in mm used directly as the size (52, 54β¦)
- Korea/Japan: ho numbers (1, 13β¦)
Measuring at home
1. From an existing ring: measure the inner diameter in mm β the most accurate method. 2. String/paper strip: wrap around the finger base, mark where it meets, measure the length (circumference). Don't pull tight β it reads small.
Reducing error
- Finger size changes through the day; measure in the evening at normal body temperature.
- Large knuckles: size for what passes over the knuckle, about a half size up.
- Wide bands (6mm+) fit tighter than thin ones at the same size β go a half size up.
Frequently Asked Questions
Related Tools
Sources & References
Content last reviewed: 2026-08-22