- Convert tab: Select your starting system (US, UK letter, EU, inner diameter mm, or circumference mm). Enter the size value and click Convert to see equivalents in all five measurement systems.
- Size Chart tab: View a complete 21-row conversion table from US 3 to US 13 with UK letters (F-Z), EU sizes, diameter, and circumference.
- How to Measure tab: Three measurement methods (string/paper, existing ring, ring sizer) plus tips on timing and accuracy.
Ring Size Converter — International Ring Size Chart
Buying rings online or from international retailers requires accurate size conversion. Our Ring Size Converter instantly converts between five sizing systems — US, UK, EU, millimeter diameter, and circumference — covering 21 sizes from US 3 to US 13, all computed in your browser.
Ring Sizing Systems
US / Canadian Sizes
North American ring sizes use a numerical system from 1 to 16, with half sizes available. The most common range is US 4-10 for women and US 8-12 for men. The scale is based on the inner circumference in inches.
UK / Australian Sizes
The British system uses letters from A to Z, where each letter corresponds to a specific inner circumference. UK sizes are used in the United Kingdom, Ireland, Australia, New Zealand, and South Africa. The most common range is H-P for women and P-X for men.
EU / Asian Sizes
European ring sizes represent the inner circumference in millimeters, typically ranging from 41 to 76. This system is used across continental Europe and much of Asia. A US 7 corresponds to approximately EU 54.
Millimeter Measurements
The most precise method uses the inner diameter in millimeters. Diameter ranges from about 14mm (US 3) to 22mm (US 13). Alternatively, you can measure the circumference (44mm to 69mm).
How to Measure Your Ring Size
Method 1: String or Paper Strip
- Cut a thin strip of paper or use a piece of non-stretchy string.
- Wrap it snugly around the base of the finger you want to size.
- Mark where the ends overlap.
- Measure the length from end to mark in millimeters — this is your circumference.
- Enter this measurement in the converter using "Circumference (mm)".
Method 2: Existing Ring
- Take a ring that fits comfortably on the intended finger.
- Place it on a ruler or use calipers.
- Measure the widest part of the inner opening in millimeters — this is the inner diameter.
- Enter this in the converter using "Inner Diameter (mm)".
Method 3: Ring Sizer
Purchase a ring sizer (a set of plastic or metal sized rings) from a jewelry store or online. They cost a few dollars and provide the most accurate measurement.
tips for Accurate Sizing
- Time of day: Measure in the evening when fingers are naturally slightly swollen.
- Temperature: Cold weather shrinks fingers; hot weather expands them.
- Repeat: Measure 3-4 times across different days for the most reliable result.
- Knuckle size: The ring must slide over the knuckle. If your knuckle is significantly larger than the base of your finger, size for the knuckle and consider a ring with a comfort fit.
- Width matters: Wider bands (over 6mm) typically require a half-size larger than narrow bands.
Privacy and Security
All ring size conversions run entirely in your browser. No measurements or personal data are transmitted to any server.