Ring Size Conversions
Convert ring sizes — US, UK, EU, Japan, and inner diameter. Free charts for buying rings online from international jewelers.
4 units · 5 calculators
Ring sizes vary by country. The US uses a numeric scale; the UK uses letter sizes; EU sizes often reflect inner circumference in mm; Japan uses its own numbering.
Because sizing is standardized only within each market, buying rings abroad requires a conversion chart. We map common US sizes to UK, EU, and Japan equivalents based on published jewelry industry references.
Wide bands, comfort-fit profiles, and temperature (fingers swell in heat) all change how a ring feels. Charts map nominal sizes — a jeweler can measure inner diameter or circumference if you are between sizes.
Quick ring size calculator
Ring Size Calculator
Formulas & rules
- EU size ≈ inner circumference in mm (e.g. EU 54 ≈ 54 mm circumference).
- US sizes step in roughly 0.4 mm diameter increments between common sizes.
- Convert by chart row index, not by multiplying US size by a constant.
Popular ring size conversions
Real-world example
You know your US ring size is 7 but an Italian seller lists EU sizes. Converting via the chart points to approximately EU 54 (inner circumference ~54 mm), guiding a better online purchase.
Common mistakes
- Measuring a ring that is already on your finger with a string instead of using a mandrel or jeweler's sizer.
- Forgetting that UK letter sizes are not numeric US sizes.
- Ordering half sizes when the target market only lists whole sizes.
All ring size conversions
Ring Size units explained
- US Size (US) · base unit
- Also: us size, american
- UK Size (UK)
- Also: uk size, british
- EU Size (EU)
- Also: eu size, european
- Japan Size (JP)
- Also: japan size, japanese
Frequently asked questions
- How is EU ring size measured?
- EU sizes typically correspond to inner circumference in millimeters. US size 7 is roughly 54 mm circumference (EU 54).
- Should I size up for wide bands?
- Wide bands (6 mm+) often feel tighter. Many jewelers recommend half a size up — a physical fitting still beats chart conversion when possible.