Ring Size Converter

What Is a Ring Size Converter?

A ring size converter is a tool that translates the ring size from one country's sizing standard to another. Different countries and jewelry markets use different scales for ring sizes, which makes international shopping, gifting, or online jewelry purchases confusing. The US uses numbers (1 through 15 in half-size increments), the UK and Ireland use letters (A through Z+), Europe uses millimeter-based numbers representing the ring's inner circumference, Japan uses a numeric scale, and Brazil uses a different numeric scale.

All ring sizing systems are ultimately based on the inner circumference or diameter of the ring, which is the measurement of the finger it fits. The converter tool above uses this underlying measurement to translate accurately between systems. Enter your known ring size and select the target system, and the tool will display the equivalent size along with the inner diameter and circumference in millimeters. If you specifically need to find the mm diameter or circumference for a ring size, use our dedicated ring size to mm converter which focuses on that conversion with a full mm chart.

International Ring Size Chart

The table below shows the complete international ring size chart covering US, UK, EU, Japan, Brazil, inner diameter, and circumference. Sizes are listed from smallest to largest. Use this chart as a reference when shopping for rings internationally or when measuring a ring for sizing.

How to Measure Your Ring Size

String or Paper Method

The string or paper method is the most accessible way to measure your ring size at home. Cut a thin strip of paper or a length of string approximately 15 cm long. Wrap it snugly around the base of the finger you want to measure — the same finger and hand on which you will wear the ring. Mark or pinch the point where the paper or string overlaps to complete the circle. Lay it flat and measure the length in millimeters. This measurement is the inner circumference of the ring you need. Use the international ring size chart above to find your size in your preferred system. For example, a circumference of 54.4 mm corresponds to US size 7, UK size N, EU size 54, Japan size 14, and Brazil size 15.

For the most accurate result, measure your finger at the end of the day when fingers are at their largest, avoid measuring when fingers are cold or very warm, and wrap the strip snugly but not tightly. If your knuckle is larger than the base of your finger, measure both and choose a size between the two.

Using an Existing Ring

If you already have a ring that fits the correct finger, you can measure its inner diameter to determine your ring size. Place the ring on a flat surface and measure the inner diameter across the widest point of the inside of the ring using a ruler or digital calipers. This measurement in millimeters corresponds to the diameter column in the ring size chart above. For example, an inner diameter of 17.3 mm corresponds to US size 7, UK size N, and EU size 54.

Alternatively, trace the inner circle of the ring on paper, then measure the diameter of the circle you drew. Digital calipers provide the most accurate measurements for this method, but a standard ruler works well for most purposes.

Ring Sizer Tools

Professional ring sizers are sets of metal or plastic rings in incremental sizes used by jewelers to determine ring size. Many jewelry stores will measure your ring size for free using a ring sizer mandrel or a set of ring gauge bands. Online jewelers also frequently provide free plastic ring sizer kits upon request. For a ring intended as a gift, asking a friend who knows the recipient, or borrowing one of their rings for measurement, is often the most practical approach.

US to UK Ring Size Conversion

The US ring sizing system uses numbers in half-size increments starting from size 1, with the most common women's sizes ranging from 5 to 8 and men's sizes ranging from 8 to 12. The UK system uses letters of the alphabet with half-size increments (e.g., N, N½, O). A US size 7 ring is approximately equivalent to a UK size N, EU 54, Japan 14, and Brazil 15. A US size 6 corresponds to UK L, EU 51.5, Japan 12, and Brazil 13. A US size 8 corresponds to UK P, EU 57, Japan 16, and Brazil 17.

The UK system covers a wider range of letters to accommodate more precise half-size steps. UK sizes available through half-step increments include F½, G, G½, H, H½, I, I½, J, J½, K, and so on. When converting, use the tool above for precise matching, as the relationship between US numbers and UK letters is not perfectly linear due to differences in how each system was historically calibrated. If you only need to convert between US and UK sizes, use our dedicated US to UK ring size converter for a focused conversion with full chart.

US to EU Ring Size Conversion

The European ring size system is also called the ISO standard system and measures the inner circumference of the ring in millimeters. A US size 7 ring has an inner circumference of approximately 54.4 mm, making its EU equivalent size 54. A US size 6 is approximately EU 51.5, and a US size 8 is approximately EU 57. EU sizes increase in roughly 1.3 mm steps, corresponding to the approximately 1.3 mm circumference difference between each half-size increment in the US system.

The EU system is particularly useful because it directly corresponds to a physical measurement, making it easier to verify with a string and ruler measurement. If you measure your finger circumference as 53 mm, your EU size is 53, which corresponds to approximately US 6.5, UK M, Japan 13, and Brazil 14.

Brazil to US Ring Size

Brazilian ring sizes use a numeric system starting from size 7, with sizes increasing in whole number increments. The Brazilian system is similar to the Japanese system but uses different starting numbers. A Brazil size 15 corresponds to US size 7, UK N, EU 54, and Japan 14. A Brazil size 11 corresponds to US size 5, and a Brazil size 21 corresponds to US size 10. When shopping on Brazilian jewelry websites or ordering from Brazilian jewelers, use the converter above to find the correct Brazilian size for your US, UK, or EU ring size.

Tips for Getting the Right Fit

Ring sizing can vary slightly between jewelers, manufacturers, and countries due to differences in production standards. Wide bands require a larger size than narrow bands because they take up more surface area on the finger. As a general rule, go up by half a size for bands wider than 6 mm. Fingers are slightly larger in warm weather and in the evening, and slightly smaller in cold weather and in the morning. Measure at different times of day and take the average for the best result.

If you are between sizes, it is generally better to size up for comfort, especially for rings worn daily. Rings can always be resized by a jeweler, though some ring designs (eternity bands, tension-set rings, and rings with stones all the way around) cannot be easily resized. Always confirm the sizing policy with the retailer before purchasing rings online internationally.

Frequently Asked Questions