💍 Ring Size Converter
Ring systems measure the same thing differently: a US 7 is a UK N and an EU/ISO 54.4 — all describing a 17.3 mm inner diameter. Convert below — everything happens on your device.
US / CA
7
UK / AU
N
EU / ISO
54.5
Diameter
17.35 mm
Circumference
54.5 mm
Between sizes or a wide band (>6 mm)? Choose the larger size.
How to measure
- Wrap a strip of paper or string snugly around the base of your finger (measure at the end of the day, when fingers are largest).
- Mark where it overlaps and measure the length in millimeters — that is your finger circumference, and directly your EU/ISO size.
- Enter it in the converter (or measure an existing ring’s inner diameter instead) — the nearest size in every system appears instantly.
- Between two sizes, or a wide band (>6 mm)? Choose the larger size.
The EU/ISO 8653 standard sizes rings by inner circumference in millimeters, which is why measuring with a paper strip gives you the EU size directly. US numeric and UK letter sizes are fixed steps on the same scale — one UK letter per half US size. Knuckle larger than the finger base? Measure both and pick between them.
Full international ring size chart
| US / CA | UK / AU | EU / ISO | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|
| 3 | F | 44.2 | 14.07 | 44.2 |
| 3.5 | G | 45.5 | 14.48 | 45.5 |
| 4 | H | 46.8 | 14.89 | 46.8 |
| 4.5 | I | 48.1 | 15.3 | 48.1 |
| 5 | J | 49.4 | 15.71 | 49.4 |
| 5.5 | K | 50.6 | 16.12 | 50.6 |
| 6 | L | 51.9 | 16.53 | 51.9 |
| 6.5 | M | 53.2 | 16.94 | 53.2 |
| 7 | N | 54.5 | 17.35 | 54.5 |
| 7.5 | O | 55.8 | 17.76 | 55.8 |
| 8 | P | 57.1 | 18.17 | 57.1 |
| 8.5 | Q | 58.4 | 18.58 | 58.4 |
| 9 | R | 59.7 | 18.99 | 59.7 |
| 9.5 | S | 60.9 | 19.4 | 60.9 |
| 10 | T | 62.2 | 19.81 | 62.2 |
| 10.5 | U | 63.5 | 20.22 | 63.5 |
| 11 | V | 64.8 | 20.63 | 64.8 |
| 11.5 | W | 66.1 | 21.04 | 66.1 |
| 12 | X | 67.4 | 21.45 | 67.4 |
| 12.5 | Y | 68.7 | 21.86 | 68.7 |
| 13 | Z | 70 | 22.27 | 70 |
Frequently asked questions
How do I measure my ring size at home?
Wrap a strip of paper snugly around the base of the finger, mark the overlap, and measure the length in mm. That circumference is your EU/ISO size; the converter maps it to US and UK instantly. Measure late in the day and size up if between sizes.
What is a US ring size 7 in UK and EU?
US 7 = UK/AU N = EU/ISO 54.4 (a 17.3 mm inner diameter). The full chart on this page covers US 3–13.
How accurate are string measurements?
Within about half a size when done snugly — string stretches, so paper is better. For an important purchase (engagement rings!), confirm with a jeweler’s sizer or measure a well-fitting ring’s inner diameter.
Are men’s and women’s ring sizes different systems?
No — the scales are identical. Typical ranges differ (women commonly US 5–8, men US 8–12), but a US 9 is the same physical size for anyone.
Is this ring size converter private?
Yes — it runs entirely in your browser. Sizes and body measurements are never sent to a server, logged or stored, and the page works offline.