What is a US size 7 in EU sizes?
An EU 54. The inside circumference is 54.4 mm, and the EU size is the circumference rounded, so EU 54. The inside diameter is 17.3 mm and the UK equivalent is N½.
US ring size to EU conversion
European sizing barely needs converting. The EU size is the inside circumference in millimetres, which means you can measure it directly.
Ring size calculator
Enter your finger circumference — that number is already your EU size.
Your size
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Enter a measurement in millimetres
Part of a larger guide
This page covers one conversion corridor in depth: US numbers to EU/ISO sizes. For a complete overview, see how every sizing system is built.
European sizing is the easiest system in the world to understand, because it barely is a system. The EU size is the inside circumference of the ring in millimetres. An EU 54 ring measures 54 mm around the inside. That is the whole rule.
This is codified in ISO 8653, and it is why European sizes are numbers in the fifties and sixties while US sizes are numbers under 15. They are not the same kind of number at all: the US figure is an arbitrary label, the EU figure is a measurement.
The practical consequence
If you measure your finger circumference with a paper strip and get 54 mm, you have just directly measured your EU ring size. No conversion, no chart, no lookup. How to take that measurement
The conversion chart
| US / Canada | EU / ISO | Inside circumference | Inside diameter | UK / AU / IE |
|---|---|---|---|---|
| 3 | 44 | 44.2 mm | 14.1 mm | F |
| 3.5 | 45–46 | 45.5 mm | 14.5 mm | G |
| 4 | 47 | 46.8 mm | 14.9 mm | H |
| 4.5 | 48 | 48.0 mm | 15.3 mm | I |
| 5 | 49 | 49.3 mm | 15.7 mm | J½ |
| 5.5 | 50–51 | 50.6 mm | 16.1 mm | K½ |
| 6 | 52 | 51.9 mm | 16.5 mm | L½ |
| 6.5 | 53 | 53.1 mm | 16.9 mm | M½ |
| 7 | 54 | 54.4 mm | 17.3 mm | N½ |
| 7.5 | 56 | 55.7 mm | 17.7 mm | O½ |
| 8 | 57 | 57.0 mm | 18.1 mm | P½ |
| 8.5 | 58 | 58.2 mm | 18.5 mm | Q½ |
| 9 | 59–60 | 59.5 mm | 18.9 mm | R½ |
| 9.5 | 61 | 60.8 mm | 19.4 mm | S½ |
| 10 | 62 | 62.1 mm | 19.8 mm | T½ |
| 10.5 | 63 | 63.4 mm | 20.2 mm | U½ |
| 11 | 64–65 | 64.6 mm | 20.6 mm | V½ |
| 11.5 | 66 | 65.9 mm | 21.0 mm | W½ |
| 12 | 67 | 67.2 mm | 21.4 mm | X½ |
| 12.5 | 68–69 | 68.5 mm | 21.8 mm | Y½ |
| 13 | 70 | 69.7 mm | 22.2 mm | Z½ |
Why some EU sizes are shown as a range
US sizes do not land on whole millimetres. US 9 has a circumference of 59.5 mm, which is exactly between EU 59 and EU 60. Retailers genuinely stock both, and neither is more correct.
Where you see a range in the chart, either size will be within about half a millimetre of your finger — well inside the tolerance of most home measurements. If you can, pick based on the rest of your judgement: go to the larger figure if your knuckle is prominent, the band is wide, or you tend to run warm.
Converting an EU size to US
Because the EU size is a measurement, you can go straight from it to a US size without any special knowledge:
- Take the EU number as millimetres of circumference EU 54 means 54 mm.
- Find the closest circumference in the chart 54 mm is nearest US 7, which is 54.4 mm.
- Or divide by pi for the diameter 54 ÷ 3.1416 = 17.2 mm, which is essentially the 17.3 mm listed for US 7.
Which countries use this system?
Most of continental Europe, including Germany, France, Scandinavia, the Netherlands and Poland, uses the ISO circumference size. French listings sometimes describe it as the "tour de doigt", which is simply the finger circumference.
A few European countries use a related but different scale. Italy, Spain and Switzerland commonly use the circumference minus 40 — so an ISO 54 appears as a 14. If you are ordering from an Italian or Spanish jeweller and the sizes look implausibly small, that is likely what you are seeing. Add 40 to get back to the circumference.
Check which European scale a retailer means
A listing showing "size 14" from an Italian seller is probably ISO 54 — a US 7. The same "14" from a Japanese seller means something different again. When a number is ambiguous, ask the retailer for the inside diameter or circumference in millimetres. That figure means the same thing everywhere.
Half sizes in the EU system
Because the scale is a direct measurement, European half sizes are literally half a millimetre: EU 54.5 is a 54.5 mm circumference. Not every retailer stocks them, but the notation is unambiguous when they do.
This is a genuine advantage of the system. A US half size is 1.25 mm — a meaningful jump — whereas a European retailer offering half sizes is offering increments less than half that. If you sit awkwardly between US sizes, buying from a European seller in ISO sizing may get you a closer fit than the US scale allows. More on being between sizes
Ordering from a European retailer
Give them your circumference in millimetres. It is their native unit, it needs no conversion, and it removes every opportunity for a mistake. If you only know your US size, look up the circumference in the chart above and quote that instead of the number.
How reliable are these conversions?
The millimetre figures are consistent and checked, but the size labels attached to them are convention rather than enforced standard. Published charts vary between manufacturers by up to roughly a quarter of a size. When precision matters, quote the inside circumference in millimetres and use the retailer's own chart rather than a general one.
US and EU conversion questions
What does EU ring size 54 mean?
It means the ring has an inside circumference of 54 millimetres. European sizing follows ISO 8653, where the size is the measurement rather than a code, so no conversion is needed to interpret it. That corresponds to a US 7.
How do I convert my finger measurement to an EU size?
You do not need to. If you measure your finger circumference in millimetres, that figure is your EU size. A 54 mm circumference is an EU 54. This is the only major system where the measurement and the size are the same number.
Why do Italian and Spanish ring sizes look different?
Italy, Spain and Switzerland commonly use the circumference minus 40, so an ISO 54 is listed as a 14. If sizes from a Southern European retailer look implausibly small, add 40 to get the circumference in millimetres.
Are EU half sizes available?
Yes, and because the scale is a direct measurement a European half size is literally half a millimetre — an EU 54.5 is a 54.5 mm circumference. Not every retailer stocks them, but where they do, the increments are finer than US half sizes, which are 1.25 mm apart.
Where to go next
US to UK letters
A genuinely unrelated scale that needs a real lookup table.
Every sizing system comparedJapan, India, Switzerland and the rest, and the logic behind each.
Measure your circumferenceThe measurement that is already an EU size.
The full millimetre chartAll systems side by side, from US 3 to US 13.