MM to Ring Size Converter
Convert millimeter measurements to international ring sizes
Ring Size Converter
Conversion Mode
Millimeter to Ring Size
Convert finger measurements in mm to ring sizes
Measure your finger with string or paper strip
Ring Size Conversion
Convert between different country sizing systems
Enter the size in the selected country's system
Quick Examples:
How to Measure Your Ring Size
Method 1: String or Paper Strip
- Cut a strip of paper or get a piece of string
- Wrap it around the base of your finger
- Mark where the paper/string overlaps
- Measure the length with a ruler in millimeters
- Enter this measurement as "Circumference" in the calculator
Tip: Measure your finger at the end of the day when it's largest.
Method 2: Existing Ring
- Place an existing ring on a ruler
- Measure the inside diameter in millimeters
- Enter this measurement as "Diameter" in the calculator
Note: Make sure the ring fits the same finger you're sizing for.
Popular Ring Sizes
Measurement Tips
Measure at the end of the day when fingers are largest
Choose the next size up if between sizes
Consider ring width - wider rings need larger sizes
Measure the specific finger where you'll wear the ring
Temperature affects finger size - avoid measuring when very cold
Complete Ring Size Chart
| Diameter (mm) | Circumference (mm) | US & Canada | UK & Australia | France & Russia | Germany | Japan | Switzerland |
|---|---|---|---|---|---|---|---|
| 11.53 | 36.22 | 0 | — | — | — | — | — |
| 11.95 | 37.54 | 1/2 | A | — | — | — | — |
| 12.37 | 38.86 | 1 | B | — | — | 1 | — |
| 12.78 | 40.15 | 1 1/2 | C | — | — | — | — |
| 13.21 | 41.5 | 2 | D | 41 1/2 | 13 1/2 | 2 | 1 1/2 |
| 13.61 | 42.76 | 2 1/2 | E | 42 3/4 | 13 3/4 | 3 | 2 3/4 |
| 14.05 | 44.14 | 3 | F | 44 | 14 | 4 | 4 |
| 14.36 | 45.11 | 3 3/8 | G | 45 1/4 | — | 5 | 5 1/4 |
| 14.45 | 45.4 | 3 1/2 | G 1/4 | — | 14 1/2 | — | — |
| 14.56 | 45.74 | 3 5/8 | G 1/2 | — | — | 6 | — |
| 14.65 | 46.02 | 3 3/4 | H | 46 1/2 | — | — | 6 1/2 |
| 14.86 | 46.68 | 4 | H 1/2 | — | 15 | 7 | — |
| 15.04 | 47.25 | 4 1/4 | I | 47 3/4 | — | — | 7 3/4 |
| 15.27 | 47.97 | 4 1/2 | I 1/2 | — | 15 1/4 | 8 | — |
| 15.4 | 48.38 | 4 5/8 | J | 49 | 15 1/2 | — | 9 |
| 15.7 | 49.32 | 5 | J 1/2 | — | 15 3/4 | 9 | — |
| 15.8 | 49.64 | 5 1/8 | K | 50 | — | — | 10 |
| 16 | 50.27 | 5 3/8 | K 1/2 | — | — | 10 | — |
| 16.1 | 50.58 | 5 1/2 | L | 51 3/4 | 16 | — | 11 3/4 |
| 16.51 | 51.87 | 6 | M | 52 3/4 | 16 1/2 | 12 | 12 3/4 |
Note: This table shows the first 20 sizes. Our calculator includes all standard sizes from 0 to 13+ US.
Understanding Ring Size Conversion
International Sizing Systems
Different countries use different ring sizing systems. Our converter supports all major international standards and provides accurate conversions between them.
Why Accurate Sizing Matters
- •Ensures comfortable daily wear
- •Prevents rings from falling off
- •Avoids costly resizing
- •Essential for online jewelry purchases
Conversion Formula
Circumference to Diameter
Diameter = Circumference ÷ π (3.14159)
Diameter to Circumference
Circumference = Diameter × π (3.14159)
Size Selection
Always choose the next size up when your measurement falls between standard sizes.
Example: 54mm Circumference
Measurement
- Circumference: 54.0 mm
- Closest standard: 54.51 mm
- Diameter: 17.35 mm
- Rule: Choose next size up (54.51 mm)
International Sizes
- US & Canada: Size 7
- UK & Australia: Size O
- France & Russia: Size 55 1/4
- Germany: Size 17 1/4