Ring size guide
Updated: 14 July 2026
In Europe the ring size is the inside circumference of the ring in millimeters. A ring with a 52 mm circumference is size 52 and has an inside diameter of 16.6 mm. The most accurate ways to find your size are a ring you already wear or a visit to a jeweler. Below you get both, the conversion chart and a fallback for when you have neither.
Ring size chart
| Circumference (EU) | Diameter | US | UK |
|---|---|---|---|
| 48 mm | 15.3 mm | US 4.5 | UK I |
| 49 mm | 15.6 mm | US 5 | UK J |
| 50 mm | 15.9 mm | US 5.5 | UK K |
| 51 mm | 16.2 mm | US 5.5 | UK L |
| 52 mm | 16.6 mm | US 6 | UK M |
| 53 mm | 16.9 mm | US 6.5 | UK M |
| 54 mm | 17.2 mm | US 7 | UK N |
| 55 mm | 17.5 mm | US 7 | UK O |
| 56 mm | 17.8 mm | US 7.5 | UK P |
| 57 mm | 18.1 mm | US 8 | UK Q |
| 58 mm | 18.5 mm | US 8.5 | UK Q |
| 59 mm | 18.8 mm | US 9 | UK R |
| 60 mm | 19.1 mm | US 9 | UK S |
| 61 mm | 19.4 mm | US 9.5 | UK T |
| 62 mm | 19.7 mm | US 10 | UK T |
| 63 mm | 20.1 mm | US 10.5 | UK U |
| 64 mm | 20.4 mm | US 11 | UK V |
Measure a ring you already own
This is the most reliable method at home. Take a ring that sits well on the right finger and measure the inside diameter. Lay the ring on a ruler and measure from inside edge to inside edge in millimeters.
To get the circumference from the diameter, multiply by 3.1416. A diameter of 16.6 mm gives about 52 mm of circumference, so size 52.
Ring sizer or jeweler
A ring sizer (multisizer) is more precise. It is a set of sample rings in every size and costs very little online. You try the sizes until one sits comfortably and still passes your knuckle.
The most accurate way is to have a jeweler measure your finger. It takes a minute and costs nothing. For an expensive ring or a surprise, that minute is worth it.
No ring to hand: the string method
No ring, no sizer and no time for a jeweler? The string method gives you a rough estimate. It is an estimate and nothing more, so do not buy an expensive ring on it alone.
- Wrap a thin string or a paper strip around the finger, where the ring will sit.
- Mark the point where the string meets itself.
- Measure the length up to the mark with a ruler, in millimeters. That is roughly your circumference.
To keep the estimate usable: do not stretch the string. The ring also has to pass your knuckle, so check that too. Wide bands feel tighter, so go a size up for those. Fingers are thicker in the evening and in warm weather than in the morning or in the cold. Measure a few times on different days and take the middle value.
US and UK sizes
Other countries use other systems. The US uses numbers with half steps, the UK uses letters. Size 52 is about US 6 and UK M.
The conversion does not land on round numbers, because the systems start at different points. When in doubt, trust the measured circumference in millimeters.
Common questions
How do I measure my ring size?
The accurate ways are measuring the inside diameter of a ring that already fits, using a ring sizer, or having a jeweler measure your finger for free. The string method is only a rough fallback.
What does ring size 52 mean?
Ring size 52 means 52 mm inside circumference. That is an inside diameter of 16.6 mm.
What is ring size 52 in US sizes?
Size 52 is about US 6. US sizes run in half steps.