Interactive Utility
International Ring Size Converter
Convert any measurement or regional ring size instantly. Select your input type below or type an exact millimeter diameter to calculate equivalent global sizes.
Calculated Global Sizes
🇺🇸 US / Canada: 7
🇬🇧 UK / Australia: O
🇪🇺 Europe (ISO mm): 54
🇯🇵 Japan / Asia: 14
🇮🇳 India: 14
Inside Diameter: 17.3 mm
Inside Circumference: 54.4 mm
How Ring Size Conversions Work
Ring sizes around the globe are tied to two primary physical dimensions: the inside diameter (the distance across the circular opening of the ring) and the inside circumference (the distance around the inner edge).
Because the mathematical relation is defined by Circumference = π × Diameter, converting between systems requires mapped conversion tables or direct calculation against the international standard ISO 8653:2016.
Important Regional Sizing Notes
- US & Canada: Increments by 0.8128 mm diameter per full size, utilizing quarter and half increments.
- UK & Australia: Alphabetical scale from A to Z, where each half letter adds 0.625 mm of circumference.
- Continental Europe: Measures direct inner circumference in millimeters (e.g. EU 54 = 54.0 mm circumference).
- India: Uses numerical sizes 1 to 30 mapped directly to millimeters.