Using a ring you own
- Place the ring on a flat surface.
- Measure the inside diameter through the centre.
- Enter the result in millimetres above.
Measure the inside diameter of a ring or the circumference of your finger. Get the closest UK size and international equivalents instantly.
Measure the widest point across the inside of the ring.
The converter returns the closest standard equivalent. Individual brands may vary slightly.
An existing ring that fits the same finger is usually the most reliable reference. Otherwise, measure the finger circumference.
British jewellers normally use letter sizes. The calculator therefore presents the UK letter first, while the EU result represents the ring’s inside circumference in millimetres.
US and Canadian sizes use a separate numerical scale. Italian, Spanish and Polish shop sizes are also included in the converter. These are closest equivalents: always check the seller’s own chart for an expensive or non-resizable ring.
Choose the label printed by the seller. Every option is converted through the ring’s physical inside diameter; retailer charts can still differ slightly.
Letters used in the UK, Australia and New Zealand.
ISO-style number based on inside circumference in millimetres.
Numbers and half sizes used in the United States and Canada.
Italy, Spain and Poland commonly use the EU circumference number minus 40.
A diameter-based size, usually shown in whole or half millimetres.
Japanese JCS numbers, also commonly listed in Singapore.
Hong Kong has its own numerical jewellery scale.
Mainland Chinese shop sizes are not the same as Hong Kong sizes.
Swiss numbers follow a separate quarter-step conversion table.
Fingers are often slightly larger in the evening than first thing in the morning.
Cold can shrink fingers; hot weather and exercise can make them swell.
The ring must pass over the knuckle without spinning loosely at the base.
Bands around 5 mm or wider often need the next size up for comfort.
Practical answers about UK sizes, measuring and fit.
The conversion anchors are checked against published jeweller charts; retailer availability and half-size labelling may differ.