Full Ring Size Chart
See the main reference page and full comparison table.
Ring Size Chart in MM
Find ring size by inside diameter or circumference in millimeters, then compare US, UK, EU, and JP size systems in the same row.
Diameter in mmCircumference in mmUS, UK, EU and JP
Visual MM reference
Use the visual chart for quick reference. The full table below provides detailed size lookup.
Ring Size Chart in MM Table
Use this full millimeter table to map diameter and circumference to major ring size systems.
| US | UK | EU | JP | Inside Diameter (mm) | Inside Circumference (mm) |
|---|---|---|---|---|---|
| 3.0 | F | 44 | 4 | 14.05 | 44.14 |
| 3.5 | G | 45 | 5 | 14.45 | 45.40 |
| 4.0 | H 1/2 | 47 | 7 | 14.86 | 46.68 |
| 4.5 | I 1/2 | 48 | 8 | 15.27 | 47.97 |
| 5.0 | J 1/2 | 49 | 9 | 15.70 | 49.32 |
| 5.5 | K 1/2 | 50 | 10 | 16.10 | 50.58 |
| 6.0 | L 1/2 | 52 | 12 | 16.51 | 51.87 |
| 6.5 | M 1/2 | 53 | 13 | 16.92 | 53.16 |
| 7.0 | N 1/2 | 54 | 14 | 17.35 | 54.51 |
| 7.5 | O 1/2 | 56 | 16 | 17.75 | 55.76 |
| 8.0 | P 1/2 | 57 | 17 | 18.19 | 57.15 |
| 8.5 | Q 1/2 | 58 | 18 | 18.53 | 58.21 |
| 9.0 | R 1/2 | 59 | 19 | 18.89 | 59.34 |
| 9.5 | S 1/2 | 61 | 21 | 19.41 | 60.98 |
| 10.0 | T 1/2 | 62 | 22 | 19.84 | 62.33 |
| 10.5 | U 1/2 | 63 | 23 | 20.20 | 63.46 |
| 11.0 | V 1/2 | 64 | 24 | 20.68 | 64.97 |
| 11.5 | W 1/2 | 66 | 26 | 21.08 | 66.23 |
| 12.0 | Y | 67 | 27 | 21.49 | 67.51 |
| 12.5 | Z | 68 | 28 | 21.89 | 68.77 |
| 13.0 | Z+1 | 69 | 29 | 22.33 | 70.15 |
Measurements are approximate and can vary slightly by jeweler, ring width, and sizing system.
Diameter vs Circumference in MM
- Diameter is measured across the inside of a ring.
- Circumference is measured around the finger or ring interior.
- Both values can map to ring size rows.
- Millimeters are usually the most precise unit for matching.
For step-by-step measuring methods, read how to measure ring size.
MM to Ring Size Calculator
If you already have a millimeter measurement, use the calculator to find the closest standard size quickly.
Common MM Measurements
- 16.5 mm is close to US 6.
- 17.3 mm is close to US 7.
- 18.2 mm is close to US 8.
- 19.8 mm is close to US 10.
How to Measure in Millimeters
- For an existing ring, measure inner diameter in mm.
- For a finger, measure circumference in mm.
- Use a ruler or caliper where possible.
- Repeat measurements for better accuracy.
See how to measure ring size and printable ring sizer for measurement help.
MM, CM, and Inches
- MM is best for precision.
- Convert cm to mm by multiplying by 10.
- Convert inches to mm by multiplying by 25.4.
- The calculator handles these conversions automatically.
Go to the ring size calculator to convert and match values.
Related Ring Size Tools
Ring Size Calculator
Match diameter or circumference to nearest size.
Ring Size Converter
Convert between US, UK, EU, and JP labels.
Printable Ring Sizer
Print a sizing guide for at-home checks.
How to Measure Ring Size
Follow practical diameter and circumference steps.
Ring Size Chart in MM FAQ
How do I find ring size in mm?
Measure inside diameter of a ring or finger circumference in millimeters, then match the nearest row in the chart.
Is ring size measured by diameter or circumference?
Both can be used. Diameter is measured across the inside of a ring, while circumference is measured around the finger or ring interior.
What ring size is 16.5 mm?
16.5 mm diameter is close to US size 6 in this chart data. Always verify with repeated measurements for final fit.
What ring size is 17.3 mm?
17.3 mm diameter is close to US size 7 in this chart data. Small variation can occur by brand and ring width.
How do I convert mm to ring size?
Use diameter or circumference in mm and map to the nearest row, or enter the value in the ring size calculator for quick matching.
Is mm more accurate than inches for ring size?
Millimeters are usually easier to read precisely, so they are commonly preferred for ring sizing.
Can I use circumference in mm to find ring size?
Yes. Circumference in millimeters can be matched directly to the chart rows just like diameter values.