Ring size chart & converter
Every major system worldwide: US/Canada, UK/Australia, EU/ISO (used in France & Germany), Japan/China/India and Italy/Spain/Switzerland — plus raw millimetres. Three ways in: convert a size you know, measure a ring on this screen, or type a measurement. EU/ISO size is the inner circumference in mm; the Italian/Swiss size is that same circumference minus 40.
Lay a ring you own flat on the screen and grow the circle until it lines up with the inside edge of the ring. Don't squeeze the phone — keep it flat.
Sizes look off? Calibrate your screen once (20 seconds)
Hold any bank card against the outline below and drag the slider until the widths match exactly. Every bank card on earth is 85.6 mm wide, so this tunes the tool to your exact screen.
How to measure
Take a ring that fits the right finger, measure the inside from edge to edge — that's the inner diameter. Use the on-screen tool above, or a ruler and the millimetres tab.
Wrap a thin strip of paper snugly around the finger, mark where it overlaps, measure the strip in mm — that's the circumference. Enter it in the millimetres tab.
Fingers are largest at the end of a warm day — measure then. The ring must pass the knuckle. For wide bands, go half a size up.
Full conversion chart
| US · CA · MX | UK · AU · NZ · IE · ZA | EU / ISO · FR · DE | JP · CN · IN | IT · ES · NL · CH | Inner Ø | Circumference |
|---|---|---|---|---|---|---|
| 3 | F | 44.2 | 4 | 4.2 | 14.1 mm | 44.2 mm |
| 3.5 | G | 45.5 | 5 | 5.5 | 14.5 mm | 45.5 mm |
| 4 | H½ | 46.8 | 7 | 6.8 | 14.9 mm | 46.8 mm |
| 4.5 | I½ | 48 | 8 | 8.0 | 15.3 mm | 48 mm |
| 5 | J½ | 49.3 | 9 | 9.3 | 15.7 mm | 49.3 mm |
| 5.5 | K½ | 50.6 | 10 | 10.6 | 16.1 mm | 50.6 mm |
| 6 | L½ | 51.9 | 12 | 11.9 | 16.5 mm | 51.9 mm |
| 6.5 | M½ | 53.1 | 13 | 13.1 | 16.9 mm | 53.1 mm |
| 7 | N½ | 54.4 | 14 | 14.4 | 17.3 mm | 54.4 mm |
| 7.5 | O½ | 55.7 | 15 | 15.7 | 17.7 mm | 55.7 mm |
| 8 | P½ | 57 | 16 | 17.0 | 18.1 mm | 57 mm |
| 8.5 | Q½ | 58.3 | 17 | 18.3 | 18.5 mm | 58.3 mm |
| 9 | R½ | 59.5 | 18 | 19.5 | 19 mm | 59.5 mm |
| 9.5 | S½ | 60.8 | 19 | 20.8 | 19.4 mm | 60.8 mm |
| 10 | T½ | 62.1 | 20 | 22.1 | 19.8 mm | 62.1 mm |
| 10.5 | U½ | 63.4 | 22 | 23.4 | 20.2 mm | 63.4 mm |
| 11 | V½ | 64.6 | 23 | 24.6 | 20.6 mm | 64.6 mm |
| 11.5 | W½ | 65.9 | 24 | 25.9 | 21 mm | 65.9 mm |
| 12 | X½ | 67.2 | 25 | 27.2 | 21.4 mm | 67.2 mm |
| 12.5 | Z | 68.5 | 26 | 28.5 | 21.8 mm | 68.5 mm |
| 13 | Z+1 | 69.7 | 27 | 29.7 | 22.2 mm | 69.7 mm |
Quick answers
Ring size guides
Frequently asked
What ring size is 17.3 mm?
A 17.3 mm inner diameter is US size 7, UK N½, EU/ISO 54.4 and Japan 14. The EU/ISO number is simply the inner circumference in millimetres.
How do I measure my ring size at home?
Either measure the inner diameter of a ring that already fits (edge to edge, in mm), or wrap a thin strip of paper around the finger, mark the overlap and measure it — that's the circumference. This page also has an on-screen sizer you can lay a ring on.
Are EU and ISO ring sizes the same thing?
Yes. The EU/ISO size is defined as the inner circumference in millimetres, so EU 54 means 54 mm around. France and Germany use this scale; Italy, Spain and Switzerland use the same number minus 40.