Ring Size Chart: US, UK & EU Sizes
Compare ring sizes between US, UK and European sizing. Use the chart below to convert ring sizes and compare inside diameter and circumference in millimeters.
Ring size conversion and measurement
You can find a ring size from an existing ring or by measuring around your finger. Use the method that is easiest for you.
International ring size chart
The chart compares commonly used US, UK and European ring sizes. Diameter refers to the inside diameter of the ring. Circumference is the distance around the inside of the ring.
| US | UK | EU | Inside diameter | Circumference |
|---|---|---|---|---|
| 4 | H½ | 47 | 14.9 mm | 46.8 mm |
| 4.5 | I½ | 48 | 15.3 mm | 48.0 mm |
| 5 | J½ | 49 | 15.7 mm | 49.3 mm |
| 5.5 | K½ | 51 | 16.1 mm | 50.6 mm |
| 6 | L½ | 52 | 16.5 mm | 51.9 mm |
| 6.5 | M½ | 53 | 16.9 mm | 53.1 mm |
| 7 | N½ | 54 | 17.3 mm | 54.4 mm |
| 7.5 | O½ | 56 | 17.7 mm | 55.7 mm |
| 8 | P½ | 57 | 18.1 mm | 57.0 mm |
| 8.5 | Q½ | 58 | 18.5 mm | 58.3 mm |
| 9 | R½ | 60 | 18.9 mm | 59.5 mm |
| 9.5 | S½ | 61 | 19.4 mm | 60.8 mm |
| 10 | T½ | 62 | 19.8 mm | 62.1 mm |
| 10.5 | U½ | 63 | 20.2 mm | 63.4 mm |
| 11 | V½ | 65 | 20.6 mm | 64.6 mm |
| 11.5 | W½ | 66 | 21.0 mm | 65.9 mm |
| 12 | X½ | 67 | 21.4 mm | 67.2 mm |
| 12.5 | Z | 68 | 21.8 mm | 68.5 mm |
| 13 | Z+1 | 70 | 22.2 mm | 69.7 mm |
International ring-size conversions are approximate. Letter-size equivalents can vary slightly between charts and manufacturers, so diameter or circumference is the most useful measurement when comparing systems.
Common US ring sizes in millimeters
If you already know your US ring size, these common sizes provide a quick reference for inside diameter and circumference.
| US ring size | Inside diameter | Circumference |
|---|---|---|
| Size 5 | 15.7 mm | 49.3 mm |
| Size 6 | 16.5 mm | 51.9 mm |
| Size 7 | 17.3 mm | 54.4 mm |
| Size 8 | 18.1 mm | 57.0 mm |
| Size 9 | 18.9 mm | 59.5 mm |
| Size 10 | 19.8 mm | 62.1 mm |
| Size 11 | 20.6 mm | 64.6 mm |
| Size 12 | 21.4 mm | 67.2 mm |
How to measure ring size using a ring
If you already own a ring that fits the intended finger, measuring its inside diameter is one of the simplest ways to estimate your ring size.
- Choose a ring that fits the correct finger comfortably.
- Place the ring on a flat surface.
- Measure straight across the inside of the ring from one inner edge to the other.
- Measure across the widest point through the center of the circle.
- Record the measurement in millimeters.
- Compare the diameter with the ring size chart above.
Do not include the thickness of the ring itself. You need the inside diameter, not the outside diameter.
How to measure your finger for ring size
If you do not have a ring to measure, you can estimate your size from the circumference of your finger.
- Wrap a narrow strip of paper or a flexible measuring tape around the base of the finger.
- Keep it snug without pulling it tightly.
- Mark where the ends meet.
- Lay the paper flat and measure the length in millimeters.
- Use the circumference column in the chart to find the closest ring size.
Your fingers can change slightly in size during the day and with temperature. Measuring more than once can give you a more useful result.
Ring diameter vs circumference
Ring diameter and circumference describe the same circle in two different ways.
Inside diameter is the straight-line distance across the inside of a ring. This is useful when you already have a ring that fits.
Inside circumference is the distance around the inside of the ring. This corresponds closely to the circumference of the finger the ring needs to fit.
The relationship between the two measurements is based on π (pi):
Circumference = diameter × π
For example, an inside diameter of approximately 17.3 mm corresponds to a circumference of approximately 54.4 mm.
How European ring sizes work
Many European ring-size systems are based closely on the ring’s inside circumference in millimeters. This makes European sizing comparatively easy to understand when you know your finger measurement.
For example, a ring with an inside circumference close to 54 mm is commonly around an EU size 54.
However, retailers and countries may use different conventions, so always check which sizing system a store uses before ordering.
How should a ring fit?
A ring should normally feel secure on your finger without being uncomfortably tight. It should pass over the knuckle with some resistance but should not require excessive force to remove.
Finger size can vary with temperature, activity and time of day. The width of the ring can also affect how it feels. Wider bands may feel tighter than narrow rings in the same nominal size.
If you are between sizes, consider the ring design and band width as well as the numerical measurement.
Ring size FAQ
Quick answers to common questions about ring sizes, measurements and international conversions.
How do I calculate my ring size?
Measure either the inside diameter of a ring that already fits or the circumference of your finger in millimeters. Compare that measurement with a ring size chart to find the closest size.
What size is a 17 mm ring?
An inside diameter of around 17 mm corresponds to a circumference of roughly 53.4 mm. Depending on the sizing system and rounding used, this is around a US size 6.5–7.
What is a size 6 ring in European sizes?
A US size 6 ring has an inside circumference of approximately 51.9 mm and is commonly around EU size 52.
What is a size 7 ring in European sizes?
A US size 7 has an inside diameter of approximately 17.3 mm and a circumference of about 54.4 mm. It is commonly around EU size 54.
What is a size 8 ring in European sizes?
A US size 8 has an inside diameter of approximately 18.1 mm and a circumference of about 57 mm. It is commonly around EU size 57.
What is a size 9 ring in European sizes?
A US size 9 has an inside circumference of about 59.5 mm and is commonly around EU size 60.
Is a size 7 ring considered big?
Ring size alone does not indicate whether a finger is unusually large or small. Finger dimensions vary considerably between people, and the correct size is simply the one that fits comfortably and securely.
Is ring size 7 cm?
No. A US ring size 7 is a size designation rather than a measurement of 7 centimeters. Its inside diameter is approximately 17.3 mm and its inside circumference is approximately 54.4 mm.
Can I measure my ring size at home?
Yes. You can measure the inside diameter of a ring that already fits or measure the circumference of your finger. For valuable or precisely fitted rings, professional sizing by a jeweler provides a more reliable measurement.
Can I measure my ring size with my phone?
Some apps and websites use the phone screen as a reference for measuring an existing ring. Their accuracy depends on correct screen calibration. A physical ruler, caliper or professional ring sizer is generally a more dependable reference.
What if I am between two ring sizes?
Consider the width and design of the ring as well as how tightly you prefer it to fit. Wider bands can feel tighter than narrow bands. If available, trying both sizes is the most reliable approach.
How tight should a ring be?
A ring should feel secure without causing discomfort. It should usually slide over the knuckle with slight resistance and remain in place during normal movement.
Can ring sizes vary between jewelers?
Small differences can occur because of rounding, manufacturing tolerances and the sizing standards being used. Checking the jeweler’s own size chart is useful when ordering a ring.