Ring Size Calculator
Enter one measurement or known size. The calculator returns US, UK, EU, Japan, India, diameter, and circumference from the same engine used in the app.
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 / China
- 14
- India
- 14
- Diameter
- 17.2 mm
- Circumference (mm)
- 54.0 mm
- Circumference (in)
- 2.126 in
Computed with the same conversion engine as the Ring Sizer app. Use thin band for pure chart conversion; use a wider band when you want a fit recommendation.
Measured a finger
Choose circumference and enter the string or paper length.
Measured a ring
Choose diameter and enter the inside width across the center.
Know a size
Choose US, UK, EU, or India to convert it into every system.
Get your exact size, without the jeweler
The calculator is best for converting a measurement you already have. To capture that measurement in the first place, the app reads your size right on screen and adjusts for band width, the most accurate option short of a trip to the jeweler.
Download Ring Sizer- Free
- iOS
- No sign-up
- Works offline
FAQ
What measurement should I enter?
Use inner circumference if you measured with string or paper. Use inner diameter if you measured a ring that already fits.
Should I choose a wide band?
Choose wide or extra wide when the ring band is thicker than about 6 mm. Wider bands feel tighter, so the calculator recommends a slightly larger fit.
Is this accurate enough to order a ring?
It is accurate enough for a strong home estimate when the measurement is careful. Confirm expensive or borderline sizes with a jeweler.