Ring Sizer
A free online ring sizer. Enter a measurement, or a size you already know, and read it instantly across US, UK, EU/ISO, Japan, and India. Every number is computed from the same engine as the Ring Sizer app, so it matches what you see in the app exactly.
Published by Ring Sizer · App developer: Pawel Boguta · Updated
54 mm circumference is about US 7, UK N 1/2, EU 54.
Thin band chart size, with no fit adjustment.
Converted sizes
- US / Canada
- 7
- UK / Australia
- N 1/2
- EU / ISO
- 54
- Japan
- 14
- India
- 14
- Diameter
- 17.2 mm
- Circumference (mm)
- 54.0 mm
- Circumference (in)
- 2.126 in
Uses the Ring Sizer conversion model. Measured values and nominal size conversions can round differently. Use thin band for a chart conversion. See our methodology and supported ranges.
Three ways to find your size
Measure on screen
The most accurate option short of a jeweler. The app places a ruler on your phone screen, calibrated to your exact device, and reads the size directly.
Copy a ring you own
Measure the inner diameter of a ring that fits, in millimeters, and enter it above to get the size in every system.
Paper or string
Wrap a strip around the finger, mark where it overlaps, and measure the length in millimeters as the inner circumference.
New to this? Start with the full guide on how to measure ring size or the at-home methods.
Common ring sizes
| US | Diameter | Circumference | UK | EU |
|---|---|---|---|---|
| 5 | 15.7 mm | 49.3 mm | J 1/2 | 49 |
| 6 | 16.5 mm | 51.9 mm | L 1/2 | 52 |
| 7 | 17.3 mm | 54.4 mm | N 1/2 | 54 |
| 8 | 18.1 mm | 57.0 mm | P 1/2 | 57 |
| 9 | 18.9 mm | 59.5 mm | R 1/2 | 60 |
| 10 | 19.8 mm | 62.1 mm | T 1/2 | 62 |
See the full ring size chart for every size, or check the average ring size if you are buying a gift.
Frequently asked questions
- How does an online ring sizer work?
- You give it a measurement, such as the inner diameter or circumference of a ring you already own, and it returns the matching ring size in every system. The converter above does this instantly. The Ring Sizer app goes one step further and measures the ring or finger right on your phone screen.
- Is this ring sizer free?
- Yes. The online converter is completely free with no sign-up. The iOS app is free to download with optional in-app purchases and measures on-screen for the most accurate result short of a jeweler.
- How accurate is an online ring sizer?
- A converter is only as accurate as the measurement you give it, so measure twice and average. On-screen measurement in the app is calibrated to your exact phone model, which is far more reliable than guessing or using a printed strip.
- Can I find my ring size without measuring my finger?
- Yes, if you have a ring that already fits. Measure its inner diameter in millimeters and enter it above. If you have no ring to copy, measure the finger directly with the app, a paper strip, or a piece of string.
Sources and methodology
Read our conversion rules, supported ranges, and measurement limitations.
Get your exact size, without the jeweler
This online sizer converts a measurement you already have. To find your real size in the first place, measure it right on screen and read every system at once, the most accurate option short of a trip to the jeweler, with the Ring Sizer app, free to download with in-app purchases.
Download Ring Sizer- Free download · In-app purchases
- iOS
- No sign-up
- Works offline
