🔄 What Is a Ring Size Conversion Chart?
A ring size conversion chart compares the sizing systems used in different countries. British jewellers commonly use UK letter sizes, US and Canadian retailers commonly use numbers, and European charts use numerical EU sizes. Because the labels are different, a conversion chart helps identify the closest international equivalent.
The best conversion charts also include inside diameter and circumference. Those physical measurements are useful because they describe the actual ring opening rather than a regional label. If two published charts show slightly different converted sizes, comparing the measurements can help explain the difference.
International ring-size conversions are approximate. Different jewellers may use slightly different rounding or intermediate size increments, so check the exact retailer's current chart before ordering a valuable or difficult-to-resize ring.
Convert UK, US/Canada or EU Ring Size
Choose a starting system and size to see the nearest international equivalents.
The converter uses nearest chart equivalents. Measurements are included to help when regional size increments do not line up perfectly.
Different labels can describe almost the same physical ring opening
Diameter and circumference provide the common measurement behind UK, US and EU sizing.
UK Letter System
British ring sizes commonly use letters such as K, L, M, N, O and P, often with half sizes.
US / Canada Numbers
North American ring sizes commonly use numerical values with full, half and quarter-size increments.
European Sizes
EU charts use numerical sizes and often relate closely to circumference-based measurements.
Use the ring size conversion chart below to compare UK, US/Canada and EU ring sizes alongside inside diameter and circumference. The table is designed for quick international conversion and for checking whether two regional size labels describe a similar physical ring opening.
| UK | US / Canada | EU | Diameter (mm) | Diameter (in) | Circumference (mm) | Circumference (in) |
|---|
Conversion note: International equivalents are approximate and different jewellers may publish slightly different rounded values.
Identify your starting size system
Confirm whether the size you already know is UK, US/Canada or EU. A number alone can be ambiguous without the sizing system.
Find the matching chart row
Locate your size in the appropriate column or use the converter above.
Check the physical measurement
Compare inside diameter or circumference to make sure the converted size represents a similar ring opening.
Compare the destination system
Read across the row to find the nearest UK, US/Canada or EU equivalent.
Verify the retailer's own chart
Before ordering a specific ring, check the seller's current chart because brands can use slightly different conversions.
UK Ring Size
The UK commonly uses letters, including half-letter sizes, across a broad range from very small to extended sizes.
US & Canada
The US and Canada commonly use a numerical system with whole, half and sometimes quarter-size increments.
EU Ring Size
European sizing is numerical and often tracks closely with an inside-circumference reference.
Diameter
Inside diameter is useful when measuring a round ring that already fits the intended finger.
Circumference
Inside circumference helps connect regional labels through a common physical measurement.
Nearest Equivalents
Because size increments differ, some international conversions are nearest matches rather than exact equivalents.
UK M to US and EU ring size
UK M is commonly approximately US 6 and EU 52¾ on UK jeweller conversion references. The physical reference is around 52.5 mm circumference and 16.7 mm inside diameter.
US size 7 to UK and EU ring size
US size 7 is commonly approximately UK O and EU 55¼, with an inside circumference around 55.1 mm. If the retailer shows a nearby value, compare its listed diameter or circumference.
EU size 54 to UK and US ring size
EU 54 is commonly close to UK N and US 6½ on common UK conversion charts. International equivalence should still be checked with the retailer selling the ring.
UK Q to US and EU ring size
UK Q is commonly around US 8 and EU 57¾. Physical measurements are especially useful if another chart uses an intermediate or slightly different converted label.
If you do not know a regional ring size but you have a measurement, you can still use a conversion chart. Measure a round ring that already fits across its inside diameter, then find the nearest diameter in the chart. Alternatively, use an accurate finger-sizing method and compare the circumference.
For an existing ring, measure from inner edge to inner edge through the centre. Do not include the thickness of the metal. The ring should be round; GIA notes that using an inside measurement with a standard chart requires the inside of the ring to be perfectly round.
Have a measurement instead of a size?
Use the Finger Size Calculator or UK Ring Size Calculator to find the nearest size directly.
A conversion chart is useful for comparing regional size standards, but it cannot guarantee how a finished ring will fit. The actual fit depends on the accuracy of the starting size or measurement, the band design, knuckle size and how the retailer manufactures or labels the ring.
Professional jewellers use finger-sizing gauges and ring mandrels to determine real size and fit. GIA also distinguishes narrow rings from wider bands and recommends different sizing treatment for rings wider than 4 mm, because wide bands can feel tighter.
For engagement rings, wedding bands, eternity rings, expensive jewellery or rings that cannot easily be resized, use the conversion chart to narrow the likely size and then confirm the final fit with the retailer or a professional jeweller.
- 🔢Converting a number without confirming whether it is a US, EU or another regional size.
- 📐Ignoring inside diameter or circumference when two charts show different equivalents.
- 🔄Assuming every international size has a perfect one-to-one match.
- ↔️Ignoring band width when converting for a much wider ring.
- 🛍️Ordering without checking the seller's own size chart and exchange policy.
- 💎Using only an online conversion for a valuable ring that is difficult to resize.
International conversion is especially useful when a UK shopper buys from an American or European retailer, or when a ring listing uses a sizing system different from the one you already know. Start with a confirmed size or measurement, convert it, then compare the seller's own table.
When possible, use the product's physical measurements as a cross-check. Also review resizing and return policies before purchase, particularly for eternity rings, stone-set bands and materials that may be difficult to resize.
For one-way American conversion, see US to UK Ring Size. For a broad measurement-first reference, see the Ring Size Reference Chart.
Ring Size Reference Chart
Compare ring measurements and regional size labels in a complete lookup table.
Open reference chart →US to UK Ring Size
Convert American numerical ring sizes into British letter sizes.
Open US to UK guide →UK Ring Size Calculator
Convert diameter or circumference directly to a UK letter size.
Open UK calculator →Goldsmiths Ring Size Guide
UK jeweller chart comparing UK, Europe, US and circumference measurements.
View guide ↗Ernest Jones Conversion Chart
UK jeweller chart with inside diameter, circumference, UK, US/Canada and EU sizes.
View chart ↗GIA Professional Sizing
Professional guidance on gauges, mandrels, ring measurements and wide bands.
Read guidance ↗