Why knowing your ring size matters
A ring that's too loose might slip off, while one that's too tight can feel uncomfortable. Getting the right size means comfort, security, and avoiding resizing costs later. If you're buying internationally, keep in mind that ring size conversions differ between the US, UK, EU, and JP standards.
Method 1: Use a ring sizer app
Technology makes sizing simple. With a ring sizer app, you can place an existing ring on your phone screen and match it to on-screen guides for an accurate read — fast and easy.
- 1 Install a ring sizer app for iPhone.
- 2 Place your ring on the screen and align it with the digital circles.
- 3 Note the size, then double-check once more for consistency.
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Method 2: Printable ring size chart
- 1 Print a ring size chart at 100% scale (no "fit to page").
- 2 Place your ring over the circles until the inside edge perfectly touches the line.
- 3 Verify with the printed ruler to ensure the scale printed correctly.
Tip: Measure more than once and in different lighting to avoid mistakes.
Method 3: String or paper strip method
- 1 Cut a thin strip of paper (or use string).
- 2 Wrap it around the base of the finger where you'll wear the ring.
- 3 Mark the overlap point and measure the length in millimeters.
- 4 Use a conversion chart to find your size in US/UK/EU/JP.
This method is ideal if you don't have a ring yet — or if you're trying to measure a partner's ring size secretly for a surprise.
Method 4: Measure an existing ring with a ruler
If you have a ring that fits the correct finger, you can measure its inner diameter directly with a ruler or calipers.
- 1 Place the ring flat on a table — don't hold it, as this can distort the measurement.
- 2 Using a millimeter ruler, measure the inside diameter — the widest point from one inner edge to the other.
- 3 Match your measurement to a ring size chart. For example, 17.3mm = approximately US 7 / UK N½.
This method works best with simple band rings. Rings with a wide or irregular band may give less accurate readings.
Method 5: Compare with a known-size ring
If you know the size of one ring, you can use it as a reference to measure others.
- 1 Find a ring whose size you already know (from a previous purchase, jeweler visit, or ring sizer app).
- 2 Place it on top of the ring you want to size. Compare the inner edges.
- 3 If they match closely, the sizes are similar. If there's a visible gap, the mystery ring is larger.
This is a quick estimation method — for exact sizing, use a ring sizer app or measure the diameter directly.
Pro tips for accuracy
Measure in the evening
Fingers are slightly larger at the end of the day when they're warm.
Skip post-workout
Avoid measuring right after exercise or in the cold — fingers shrink temporarily.
Measure the right finger
Left and right hand can differ. Measure the exact finger you'll wear the ring on.
Between sizes? Go larger
Choose the slightly larger size for comfort — fingers swell throughout the day.
Ring size chart: diameter to size
Once you've measured your ring's inner diameter or finger circumference, use this chart to find your size:
| Diameter (mm) | Circumference (mm) | US Size | UK Size | EU Size |
|---|---|---|---|---|
| 14.9 | 46.8 | 4 | H | 47 |
| 15.3 | 48.0 | 4.5 | I½ | 48 |
| 15.5 | 48.7 | 5 | J | 49 |
| 15.9 | 49.9 | 5.5 | K | 50 |
| 16.3 | 51.2 | 6 | L | 51 |
| 16.7 | 52.5 | 6.5 | M | 52 |
| 17.1 | 53.8 | 7 | N | 54 |
| 17.5 | 55.0 | 7.5 | O | 55 |
| 18.0 | 56.3 | 8 | P | 56 |
| 18.4 | 57.6 | 8.5 | Q | 58 |
| 18.8 | 58.8 | 9 | R | 59 |
| 19.2 | 60.1 | 9.5 | S | 60 |
| 19.6 | 61.4 | 10 | T | 61 |
| 20.0 | 62.6 | 10.5 | U | 63 |
| 20.4 | 63.9 | 11 | V | 64 |
| 21.2 | 66.4 | 12 | X | 66 |
For the complete chart including half-sizes, see our full ring size chart.
International ring size conversion
Sizes don't translate 1:1 across systems. For example, a US 7 roughly maps to a UK N; in the EU system it's measured in millimeters, and in Japan a similar size may be around JP 14. Always verify with a reliable ring size conversion guide before purchasing.
Final thoughts
You don't have to guess. With a ring sizer app, a printable ring size chart, or the string method, you can measure your ring size at home with confidence — then cross-check with an international ring size conversion before you buy.
