Find Your Perfect Ring Size
Buying a ring without knowing the size is a gamble. This calculator converts your finger circumference in mm to ring sizes in US, UK, and EU systems instantly. Just measure with string or a tape measure and get results.
When to use this calculator
- You want to buy an engagement ring but don't know your partner's size.
- Buying a ring online and need your exact size first.
- Converting your ring size from one system to another for international purchases.
- Giving a ring as a gift and need the size without spoiling the surprise.
- You're a jeweler and need a quick size reference.
Example: 56 mm circumference
- EU: size 56.
- Diameter: 56 / π = 17.8 mm.
- US: (56 - 36.5) / 2.55 = 7.6 → size 7.5.
- UK: from chart → O.
How it works
1 min readHow to measure your finger
String method
1. Cut a piece of string or paper.
2. Wrap it around your finger where the ring will go.
3. Mark where it overlaps.
4. Measure the length with a ruler in mm.
5. That's your circumference.
Using an existing ring
1. Take a ring that fits well on that finger.
2. Measure the inside diameter in mm.
3. Multiply by π (3.14) to get circumference.
Ring size conversion chart
| Circumference (mm) | EU | US | UK |
|---|---|---|---|
| 44.2 | 44 | 3 | F |
| 47.1 | 47 | 4 | H |
| 49.3 | 49 | 5 | J |
| 51.9 | 52 | 6 | L |
| 54.4 | 54 | 7 | N |
| 56.3 | 56 | 7.5 | O |
| 57.0 | 57 | 8 | P |
| 59.5 | 60 | 9 | R |
| 62.1 | 62 | 10 | T |
| 64.6 | 65 | 11 | V |
| 67.2 | 67 | 12 | X |
Important tips
Frequently asked questions
How do I measure my ring size at home?
Wrap a string or paper around the finger where you'll wear the ring. Mark where it overlaps, then measure the length with a ruler in millimeters. That measurement is your finger circumference, which you can convert to your ring size using this calculator.
What's the difference between US, UK, and EU ring sizes?
US, UK, and EU all use different numbering systems. EU sizes typically match the circumference in mm. US sizes start at 3 for smaller rings and go up to 13+. UK sizes use letters (A–Z). All three measure the same thing but use different scales.
Why does my ring size change?
Fingers swell and shrink due to heat, cold, exercise, salt intake, pregnancy, and time of day. It's normal for your size to vary by 0.5–1 full size throughout the day. Measure in the afternoon at a comfortable temperature for the most accurate result.
Can I resize a ring if it doesn't fit?
Most metal rings (gold, silver, platinum) can be resized by 1–2 sizes by a jeweler. Some materials like titanium, tungsten, and certain alloys cannot be resized. It's usually cheaper to make a ring smaller than larger.
What's the average ring size?
For women, the average US size is 6–7. For men, it's typically 9–11. However, this varies significantly by hand size, genetics, and individual factors. Always measure your actual finger rather than assuming.
Do all ring sizes fit the same way?
Most jewelers use the same standard sizing, but there can be slight variations depending on the ring's width and construction. Wider rings may fit slightly tighter than narrow ones. A conversion chart and circumference measurement in mm is most universal.
Should I choose a size up or down if I'm between sizes?
If you're between two sizes, choose the larger one, especially if the ring will be worn daily. A slightly loose ring is easier to adjust than one that's too tight. You can always add sizing beads inside if needed.
How accurate is this calculator?
This calculator uses standard industry formulas for ring size conversion. It's accurate as long as you measure your circumference correctly. For a perfect fit, consider getting professionally sized by a jeweler before ordering expensive rings.