Ring Size Converter
Convert ring sizes between US, UK, EU, mm diameter and circumference.
Ring Size Converter
Ring sizes vary slightly by country, jeweller, and chart. Use this as an estimated common equivalent.
Supports numbers, UK letters, mm, and inches.
Estimated converted ring size
L 1/2
US / Canada 6 ≈ UK / Australia L 1/2
Estimated equivalent only. Confirm with the jeweller before ordering.
Original size
6
Target system
UK / Australia
US / Canada
6
UK / Australia
L 1/2
EU / ISO
52
Japan
12
Inside diameter
16.5 mm
Inside circumference
51.8 mm
Nearest size note
Common chart equivalent
Table-based conversion
Uses common international ring size chart equivalents instead of one oversimplified formula.
Measurement support
Diameter and circumference inputs are matched to the nearest common chart size.
Fit-aware guidance
Results include approximation notes because rings vary by jeweller, band width, and style.
Dynamic Fit Insights
How Ring Size Conversion Works
Regional systems
Ring size systems are regional conventions. Some use numbers, while others use letters.
EU / ISO sizing
EU or ISO sizes are closely tied to inside circumference in millimetres.
Physical measurements
Diameter and circumference describe the actual opening inside the ring.
Nearest matching
Measured values are matched to the nearest common chart row.
Approximate results
Conversion charts are best treated as estimates, not guaranteed fit.
Jeweller confirmation
For expensive or important rings, confirm sizing with the jeweller before ordering.
US, UK, EU, Japan, Diameter, and Circumference Explained
US / Canada
US and Canadian sizes use numbers, often with half and quarter sizes.
UK / Australia
UK and Australian sizes use letters, sometimes with half-size steps.
EU / ISO
EU sizes are commonly based on inside circumference in millimetres.
Japan
Japan uses numeric ring sizes on a separate scale.
Diameter
Diameter is the straight-line width across the inside of the ring.
Circumference
Circumference is the distance around the inside of the ring.
Measuring Ring Size Accurately
Use a ring that fits
Measure the inside diameter of a ring that already fits the intended finger.
Paper or string method
A paper strip or string can estimate finger circumference, but it is only a rough guide.
Measure at the right time
Measure near the end of the day when fingers are closer to normal size.
Avoid cold or swollen fingers
Temperature and swelling can change finger size enough to affect fit.
Consider band width
Wide bands can feel tighter than thin bands and may need different sizing.
Dominant hand difference
Fingers on the dominant hand may be slightly larger.
International Ring Size Chart Notes
Charts can differ
Jewellers may round size equivalents differently.
Half sizes vary
Half sizes and quarter sizes may not exist in every sizing system.
Resizing limits
Resizing availability depends on ring material, setting, and design.
Comfort-fit bands
Comfort-fit rings may size differently from standard-fit rings.
Common Ring Size Conversion Examples
US 5
≈ UK J 1/2
≈ EU 49
≈ JP 9
US 6
≈ UK L 1/2
≈ EU 52
≈ JP 12
US 7
≈ UK N 1/2
≈ EU 54
≈ JP 14
US 8
≈ UK P 1/2
≈ EU 57
≈ JP 16
US 9
≈ UK R 1/2
≈ EU 59
≈ JP 18
US 10
≈ UK T 1/2
≈ EU 62
≈ JP 20
Formula / Table Explanation
- 1. Choose the source size system.
- 2. Match the entered size to the nearest row in the conversion table.
- 3. Return the equivalent size in the selected target system.
- 4. Show diameter and circumference when available.
- 5. Label the result as an estimated common equivalent.
Measurement formulas
Circumference = Diameter × π
Diameter = Circumference ÷ π
Ring size conversion is mostly table-based because no single universal formula converts every international ring size perfectly.
Frequently Asked Questions
Related tools