Ring Size Converter Free Online
Convert ring sizes between US numeric, UK alphabetic, EU numeric, JP, and inner diameter or circumference in millimeters. Pick your home system, see your size in every other.
All Systems
Pro — bulk batch conversion, API access, history & favorites
API access · Priority queue · Team workspace
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How It Works
Pick Your System or Ingredient
Choose your home size system, ingredient, or input mode using the dropdowns and category buttons. Defaults are sensible so you can start typing immediately.
Enter or Pick a Value
Type a number, choose a size, or use the dual inputs (e.g. ft + in or min + sec). Conversion runs as you type — no Convert button.
See Every Equivalent
Below the main result, the All Conversions panel shows your value across every supported system or unit at once — perfect for international shopping or recipe scaling.
Ring Size Converter Features
6 Systems
US numeric, UK alphabetic, EU, JP, mm diameter, mm circumference. Covers virtually every jewelry standard.
Inner Diameter
Inner ring diameter in mm is the most precise measurement — measure an existing ring with calipers and look up the size.
Circumference
Inner circumference in mm — measure your finger with a strip of paper, then look up the size in any system.
Half Sizes
US and UK use half sizes (5.5, 6.5…) where the standard physical size lies between the integer steps.
Live Conversion
Pick a system and a size, see the equivalent in every other system instantly.
100% Private
Pure client-side lookup. No data is sent anywhere.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| Full ring size conversion | ||
| Live conversion | ||
| All-systems result panel | ||
| Bulk CSV / Excel conversion | — | |
| REST API access | — | |
| Custom precision settings | — |
Frequently Asked Questions
Wrap a thin strip of paper around the base of your finger, mark where it overlaps, then measure the length in mm — that is your inner circumference. Look it up in the chart. Best done at the end of the day when fingers are slightly larger.
UK ring size N = US 6.5 = EU 53 = JP 13 = 16.9 mm inner diameter. The UK uses an alphabetic scale from A (smallest) to Z, with half sizes like N½, O½ etc.
Within ±0.5 size in any system. There is no perfectly linear mapping because the systems were defined independently — the chart shows the standard equivalents used by major jewelers.
Yes — Canada uses the same US numeric system. Mexico also uses US sizes. South America and Australia mostly use UK alphabetic sizing.
In the US, the average women's ring size is 6 (≈16.5 mm diameter); average men's is 10 (≈19.8 mm). When in doubt, gift a size 6 for women or 10 for men — most jewelers offer free resizing.