💍 Ring Size Conversion Chart 2026
Convert ring sizes instantly between US, UK/Australia, EU, Japanese, French, German, Swiss systems — plus inner diameter (mm & inches) and circumference. Includes ISO 8653 standard, how to measure at home, Pandora sizing, engagement ring guide & diameter-circumference formulas.
🔄 Ring Size Converter — Select Any System
Select any size below — all other systems update automatically. Or enter diameter / circumference in mm.
📏 Or Enter a Measurement Directly
📖 How to Use This Ring Size Converter
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1Select a Size in Any System
Use any of the seven international system dropdowns. Select your known size (e.g., "US 7" or "EU 54") and all other systems update in real time.
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2Or Enter a Measurement
If you have an existing ring, measure its inner diameter in mm with a ruler or calipers. Enter in the "Inner Diameter (mm)" field — all size systems calculate automatically. Alternatively enter circumference in mm (string-wrap method).
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3Read All Size Systems at Once
The indigo result panel shows all systems simultaneously — US, UK/AU, EU, JP, FR, German diameter, and the exact mm diameter and circumference.
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4Find Your Row in the Full Chart
The highlighted row in the full international size chart below shows your selected size across all systems side-by-side for reference.
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5Copy & Share Your Size
Click "📋 Copy" to copy all your size details to clipboard — useful for sharing with an online jeweller or saving your sizes before shopping.
📏 How to Measure Your Ring Size at Home
String / Strip Method
- Cut a thin strip of paper or non-stretchy string
- Wrap snugly around the base of the intended finger
- Mark or cut where the ends meet
- Measure the length in mm with a ruler
- This is your circumference — enter above for instant conversion
Existing Ring Method
- Find a ring that fits the correct finger perfectly
- Place it on a ruler or use digital calipers
- Measure the inner diameter in mm (inside edge to inside edge)
- Enter in the "Inner Diameter (mm)" field above
- All international sizes appear instantly
Jeweller's Ring Sizer
- Visit any local jeweller — resizing is often free
- Mandrel sizing is the most accurate method
- Professional sizers work for all finger shapes
- Best for knuckle-dominant fingers (measure largest point)
- Repeat seasonally — sizes change with temperature and age
Printable Ring Sizer
- Print a ring sizer sheet at exactly 100% scale (no "fit to page")
- Verify scale using the printed calibration bar
- Place existing ring on the circles — match the inner edge
- Read the size from the matching circle label
- Check 2–3 adjacent sizes for between-size fitting
📐 Ring Size Mathematics — Diameter, Circumference & ISO 8653
\( C = \pi \cdot d \qquad \Leftrightarrow \qquad d = \frac{C}{\pi} \)
\( C = 2\pi r \qquad \Leftrightarrow \qquad r = \frac{C}{2\pi} \qquad d = 2r \)
\( \text{EU size} = C_{\text{inner}} \;\text{(mm)} \qquad \text{e.g., EU 52} = 52\,\text{mm circumference} \)
\( d_{\text{mm}} = \frac{\text{EU size}}{\pi} \approx \frac{\text{EU size}}{3.14159} \)
\( d_{\text{inch}} = \frac{d_{\text{mm}}}{25.4} \qquad \text{(1 inch} = 25.4\,\text{mm exactly)} \)
ISO 8653:2016 is the international standard governing ring size definitions. It specifies that ring sizes are based on the inner circumference of the ring in millimetres — which is why the EU/French/Spanish system is the most mathematically transparent: EU size 52 means exactly 52 mm inner circumference, which equals a diameter of \(52/\pi \approx 16.55\,\text{mm}\).
\( \text{EU 50:} \quad d = 50/\pi = 15.92\,\text{mm} \approx \text{US size 5} \)
\( \text{EU 52:} \quad d = 52/\pi = 16.55\,\text{mm} \approx \text{US size 6} \)
\( \text{EU 54:} \quad d = 54/\pi = 17.19\,\text{mm} \approx \text{US size 7} \)
\( \text{EU 57:} \quad d = 57/\pi = 18.15\,\text{mm} \approx \text{US size 8} \)
\( \text{EU 60:} \quad d = 60/\pi = 19.10\,\text{mm} \approx \text{US size 9.5} \)
\( \text{EU 62:} \quad d = 62/\pi = 19.74\,\text{mm} \approx \text{US size 10} \)
📊 Full International Ring Size Chart
| US / CA | UK / AU | EU | JP | FR / ES | DE (mm) | CH / IT | Ø mm | Ø inch | Circ (mm) |
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🌍 How Each Country's Ring Sizing System Works
Ring size systems evolved independently across countries, and none of them decided to harmonise neatly with each other — which is why buying a ring internationally, or shopping on a foreign website, can be so confusing. Understanding the logic behind each system makes conversions both more accurate and less anxiety-inducing.
US & Canadian System
Numerical scale from 1 to 16 in ½ increments. No direct mathematical formula to mm — based on historical empirical scale. US size 6 = 16.5 mm diameter (commonly cited average women's size). Size 5 = 15.7 mm; size 7 = 17.3 mm. Half-sizes are standard; quarter-sizes exist for custom work. Used in USA, Canada, and Mexico.
UK, Australian & Irish System
Alphabetical letters A–Z, with half-sizes denoted as A½, B½, etc. (52 sizes total). Letter A = smallest (circumference ~37.8 mm); Z = largest common size (~68.5 mm). UK size M = US 6. Used throughout UK, Ireland, Australia, New Zealand, and South Africa — all jewellers in these countries use this notation.
European (EU) / ISO 8653
Numerically equal to inner circumference in mm. EU 52 = 52 mm circumference = 16.55 mm diameter. The most mathematically transparent system. Used across Germany, France (partly), Italy, Spain, Netherlands, Portugal and most of Continental Europe. Pandora, Tiffany & Co., and many luxury brands use EU sizing.
Japanese System
Numeric scale starting at 1 (inner diameter 13.0 mm = circumference 40.8 mm) going up to 30+. Each integer step ≈ +0.4 mm diameter. JP 9 ≈ US 5; JP 13 ≈ US 6.5; JP 17 ≈ US 8. Used in Japan and South Korea. Japanese sizing is broadly similar to US numbering but starts at a smaller base size.
French / Spanish System
Essentially identical to EU sizing — inner circumference in mm. French size 52 = EU 52 = 52 mm circumference. Used in France, Belgium, Netherlands, Portugal, and Spain. The French system sometimes uses slightly different size labels for half-sizes. Technically: French size = EU size (for practical purposes they are interchangeable).
German System (Diameter-Based)
Based on inner diameter in mm (not circumference). Expressed as a decimal to one place: 14.0, 14.5, 15.0, 15.5, 16.0, 16.5, 17.0, 17.5, 18.0 etc. German size 16.5 = EU 52 = US 6. Stamped directly on German jewellery as the diameter value. Swiss and Italian sizing follows a similar convention with slight offset.
🌡️ Finger Size Variation — Temperature, Time & Biology
\( \Delta C \approx \alpha_{\text{tissue}} \cdot C_0 \cdot \Delta T \)
\( \text{Typical variation during a day: } \Delta d \approx \pm 0.2\,\text{mm} \approx \pm 0.5\,\text{size steps} \)
\( T_{\text{office}} \approx 20°C \to T_{\text{hot day}} \approx 35°C: \Delta d \approx +0.2\,\text{to}\,+0.4\,\text{mm} \approx +0.5\,\text{to}\,+1\,\text{size} \)
\( T_{\text{cold winter}} \approx 0°C: \Delta d \approx -0.3\,\text{to}\,-0.5\,\text{mm} \approx -0.5\,\text{to}\,-1\,\text{size} \)
\( \text{Finger taper angle} \approx 2–4°\text{ from base to knuckle} \)
\( \Delta d_{\text{effective}} = h \cdot \tan(\theta) \approx h \times 0.035 \text{ to } 0.070 \)
\( \text{Extra size steps} \approx \Delta d / 0.4\,\text{mm per half-step} \)
\( \text{Example: } h = 8\,\text{mm band},\;\theta = 3°: \Delta d \approx 8 \times 0.052 = 0.42\,\text{mm} \approx +1\,\text{size step} \)
💎 Pandora Ring Sizes & Luxury Brand Sizing Guide
Pandora is one of the world's most popular jewellery brands, and its sizing system is based on EU/ISO 8653 — inner circumference in mm. Pandora sizes run from 44 to 68 in 2 mm increments, plus some intermediate sizes. This means Pandora size 52 is identical to EU size 52 (US size 6, UK size L½, 16.55 mm diameter). When gifting Pandora rings, knowing the recipient's EU size is the most direct conversion.
| Pandora / EU | US / CA | UK / AU | Diameter (mm) | Notes |
|---|---|---|---|---|
| 44 | 3 | F | 14.0 | Very small |
| 46 | 3.5 | G½ | 14.6 | Small |
| 48 | 4.5 | H½ | 15.3 | US size 4.5 |
| 50 | 5 | J | 15.9 | Common women's |
| 52 | 6 | L½ | 16.5 | Most popular women's |
| 54 | 7 | N | 17.2 | Average US women |
| 56 | 7.5–8 | P | 17.8 | Larger women's / small men's |
| 58 | 8.5 | Q½ | 18.5 | |
| 60 | 9.5 | S½ | 19.1 | Average US men's |
| 62 | 10 | T½ | 19.7 |
📊 Average Ring Sizes by Country, Gender & Age
| Demographic | US Size (avg) | EU Size | Diameter mm | Circumference mm |
|---|---|---|---|---|
| Women (USA/Canada) | 6–7 | 52–54 | 16.5–17.2 | 51.8–54.0 |
| Men (USA/Canada) | 9–10 | 59–62 | 18.9–19.7 | 59.4–61.9 |
| Women (UK) | 5.5–6.5 | 50–53 | 15.9–16.9 | 50–53 |
| Men (UK) | 8.5–10 | 58–62 | 18.5–19.7 | 58–62 |
| Women (Europe) | 5.5–7 | 50–54 | 15.9–17.2 | 50–54 |
| Teenagers (14–18) | 5–6 | 49–52 | 15.7–16.5 | 49–52 |
| Engagement (women) | 6–6.5 | 52–53 | 16.5–16.9 | 51.8–53.0 |