Buying a ring online or converting a size from abroad? Our free Ring Size Converter translates between US, UK and EU ring sizes in seconds — enter your size and see every equivalent, including the inside circumference in millimetres. Please note that sizes are approximate and can vary by brand.
Ring Size Converter
Sizes are approximate and vary by brand — for the best fit, get measured by a jeweller.
How to Use
- Enter your ring size in the box.
- Choose the sizing system it belongs to — US, UK or EU.
- Click Convert Size to see the matching sizes plus the inside circumference.
- Remember that conversions are approximate, so check the jeweller’s chart.
Key Features
- Converts between US, UK and EU (ISO) ring sizes.
- Shows the inside circumference in millimetres for accurate measuring.
- Covers sizes from US 4 to 13.
- Clearly labelled as approximate, since brands vary.
- Runs entirely in your browser — free with no sign-up.
FAQs
How is ring size measured?
The most common method is the inside circumference of the band in millimetres. The EU (ISO) scale uses this number directly, while the US and UK scales convert it into their own numbering and letter systems.
Are converted ring sizes exact?
No — conversions are approximate. Manufacturers round differently and band width affects fit, so always confirm with the jeweller’s own chart, especially for surprise gifts.
What is the EU ring size scale?
The EU scale follows the ISO standard: the number equals the inside circumference in millimetres. A size 54 ring measures 54 mm around the inside of the band.
Should I size up for a wide band?
Wide bands fit more snugly than narrow ones. Many jewellers suggest going up a quarter or half size for bands wider than about 6 mm.