Ring Size Chart and Converter
Convert ring sizes between US, UK, EU, and Japanese systems. Measure your finger at home and find your exact size across all international standards.
Ring Size Converter
Complete Ring Size Chart
The chart below shows the most common ring sizes across all four major sizing systems. Sizes are matched by inner circumference, which is the universal measurement that all sizing systems are based on. Scroll horizontally on mobile to see all columns.
| US | UK | EU | Japan | Diameter (mm) | Circumference (mm) |
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How to Measure Your Ring Size at Home
Measuring your ring size at home requires nothing more than a strip of paper, a ruler with millimeter markings, and a pen. The process takes about two minutes, and if you follow these steps carefully, you can get a measurement that is accurate to within half a size of what a jeweler would give you.
Cut a paper strip
Cut a strip of paper about 10mm wide and 100mm long. Regular printer paper works fine. Do not use stretchy material like thread or yarn.
Wrap around your finger
Wrap the strip around the base of the finger where you will wear the ring. Make sure it passes over the knuckle, as the ring needs to fit over the knuckle to go on and off.
Mark the overlap
Where the paper overlaps, mark a line with a pen. The strip should be snug but not tight. You should be able to slide it back and forth slightly.
Measure in millimeters
Lay the strip flat and measure from the end to the mark. This is your finger circumference in millimeters. Enter it above to find your size.
Tips for Accurate Measurement
Measure at the end of the day when fingers are at their largest. Cold temperatures make fingers shrink, so avoid measuring right after coming in from outside in winter. Take three separate measurements on different days and use the average. If you have large knuckles relative to the base of your finger, measure both the knuckle and the base and pick a size between the two. The ring needs to fit over the knuckle but should sit comfortably at the base without spinning freely.
Using an Existing Ring
If you have a ring that already fits the correct finger well, you can measure its inner diameter with a ruler. Place the ring on a flat surface and measure the widest point across the inside of the ring in millimeters. Enter that diameter in the converter above to find the corresponding sizes in all systems.
Printable Ring Sizer Guide
Place a ring you already own over the circles below. The circle that matches the inside of your ring is your size. Make sure your screen is not zoomed in or out for accurate sizing.
For screen accuracy, you can calibrate by placing a coin on screen. A US quarter is 24.26mm in diameter.
History of Ring Sizing
The practice of wearing rings dates back thousands of years, with evidence of finger rings found in ancient Egyptian tombs dating to around 2500 BCE., standardized ring sizing is a relatively modern invention. For most of human history, rings were either custom-made by a local metalsmith who would measure the customer's finger directly, or they were adjustable bands that could be bent to fit (Ring (jewellery)).
The modern ring sizing system emerged in the 19th century as jewelry manufacturing became industrialized. When rings started being mass-produced in standard sizes rather than individually crafted, there needed to be a consistent way to label and categorize sizes. Different countries developed their own systems independently, which is why we have the American numerical system, the British alphabetical system, and the European millimeter-based system all in use today.
The American ring size system was formalized by jewelers' trade associations in the late 1800s. It assigns whole and half number sizes starting from size 0 (which has a 11.63mm inner diameter) and increasing in increments that correspond to roughly 0.8mm of diameter per full size. The British system assigns letters of the alphabet to size ranges, with A being the smallest and Z being the largest. The European system takes the most straightforward approach by simply using the inner circumference in millimeters as the size number, so there is no conversion formula needed between measurement and size label.
In Japan, the ring sizing system was established by the Japan Jewellery Association and uses a numbered scale from 1 to 30. Japanese sizes map to the same physical dimensions but use their own numbering convention. Understanding the history behind these systems helps explain why conversion charts are necessary and why there is no single universal ring size standard (Ring size).
Sizing Systems Explained
US and Canadian System
The American and Canadian system uses numbers from approximately 0 to 16, with half sizes and sometimes quarter sizes available. Each full size increase corresponds to an increase of about 2.55mm in circumference or about 0.81mm in diameter. The system was so that common adult sizes fall in a memorable range: 5 to 8 for women and 8 to 12 for men. This is the system used by most online retailers in North America and is the most commonly referenced system in English-language jewelry guides.
UK and Australian System
The British system assigns letters from A through Z, with half sizes available. Size A corresponds to roughly a US 0.5, and the sizes increase through the alphabet. The jump between each letter is approximately the same as a half size in the US system. Most adult women wear sizes H through P, while most adult men wear sizes P through Z. If you see ring sizes listed with letters, the seller is almost using the British system, which is also standard in Australia, New Zealand, Ireland, and South Africa.
European System
The European system, used across continental Europe, is the simplest to understand. The size number equals the inner circumference of the ring in millimeters, rounded to the nearest whole number or half number. A European size 52 means the ring has an inner circumference of 52mm. There is no conversion formula needed between the measurement and the size label. This system is used in France, Germany, Italy, Spain, the Netherlands, and most other European countries, though some Scandinavian countries have historically used slightly different conventions. Italian and Swiss sizes sometimes differ from the standard European system by a small offset.
Japanese System
Japan uses a numbered system established by the Japan Jewellery Association. Sizes run from 1 to about 30, with size 1 corresponding to roughly a US size 1 and an inner circumference of about 40.8mm. Each Japanese size increment corresponds to about 1mm increase in circumference. The Japanese system is also sometimes used in other East Asian markets, though China and Korea have their own sizing conventions. If you are shopping from Japanese retailers online, this is the system their listings will use.
Ring Buying Tips
Knowing your ring size is just one piece of the puzzle when buying a ring, especially if you are shopping online or buying a surprise gift for someone else. Here are practical tips gathered from jewelers and frequent ring shoppers.
Ordering from International Retailers
If you are ordering from an overseas retailer, always convert to the sizing system they use before placing your order. A "size 6" in the US system is completely different from a "size 6" in the Japanese system. Look for the retailer's size guide and check which system they are using. If in doubt, contact customer service and provide your measurement in millimeters, which is universal.
Band Width and Fit
Wider bands require a larger size than narrow bands. If you have been measured for a standard 2mm to 4mm band but are purchasing a 6mm or 8mm wide band, go up half a size. For very wide bands (10mm or more), go up a full size. The wider the band, the more surface area is in contact with your finger, which creates a tighter feel even at the same inner circumference. This catches many first-time ring buyers off guard, especially men buying their first wedding band, which tends to be wider than the jewelry they may have tried on previously.
Comfort Fit vs Standard Fit
Comfort fit rings have a slightly domed interior surface rather than a flat one. This rounded interior makes the ring easier to slide on and off over the knuckle and generally feels more comfortable for daily wear. A comfort fit ring in the same labeled size will feel slightly looser than a standard (flat interior) ring because the domed surface reduces the contact area with your finger. If you are ordering a comfort fit ring, you can usually stay true to your measured size or even go down a quarter size if you prefer a snug fit (Ring Size Guide).
Community Questions
How to programmatically convert between ring size systems?
Developers building e-commerce platforms for jewelry often implement ring size conversion. This discussion covers the mathematical relationships between the US, UK, and EU systems and how to code a reliable converter.
View on Stack OverflowAccurate rendering of circles at physical dimensions on screen
Building on-screen ring sizers requires knowing the display's pixel density (DPI) to render circles at accurate physical sizes. The answers cover how to detect and calibrate screen DPI using JavaScript.
View on Stack OverflowLookup table vs formula for ring size conversion
There is an ongoing discussion about whether ring size conversions should use a mathematical formula (since the relationship is approximately linear) or a lookup table (since official sizes do not follow a perfectly linear progression). The consensus favors lookup tables for accuracy.
View on Stack OverflowVideo Tutorials
Helpful Videos on Ring Sizing
Visual walkthrough of the paper strip method and existing ring method, with tips for getting accurate results.
Explains the differences between international sizing systems and how to convert between them when shopping online.
Creative methods for finding your partner's ring size without giving away the surprise, from borrowing an existing ring to the soap impression technique.
Frequently Asked Questions
There are several reliable methods to measure your ring size at home. The most accurate DIY method is the string or paper strip method. Cut a thin strip of paper or a piece of non-stretchy string about 6 inches long. Wrap it around the base of the finger you size, making sure it passes over your knuckle comfortably. Mark where the strip overlaps with a pen. Lay the strip flat and measure the distance from the end to the mark in millimeters. This measurement is the circumference of your finger. Compare it to a ring size chart to find your size. For the most accurate results, measure your finger at the end of the day when your fingers are at their largest, and measure 3-4 times to get a consistent reading. Avoid measuring when your hands are cold, as fingers shrink in cold temperatures and expand in warm conditions.
The most common ring size for women in the United States falls between size 5 and size 7, with size 6 being the most frequently purchased size. This corresponds to an inner diameter of approximately 16.5mm and a circumference of about 51.8mm. In the UK system, that translates to roughly size L or M, and in the European system, it is approximately size 51 or 52. Of course, ring size varies significantly between individuals based on factors like body type, genetics, age, and even climate. Women who are taller or have larger hands may wear a size 7 to 9, while petite women might wear a size 4 to 5. If you are buying a surprise engagement ring and cannot measure your partner's finger directly, size 6 is the safest statistical guess for women, but borrowing a ring they already wear on that finger is a much more reliable approach.
For men in the United States, the most common ring sizes range from size 8 to size 12, with sizes 9 and 10 being the most frequently purchased. A US size 10 has an inner diameter of about 19.8mm and a circumference of roughly 62.1mm. In the UK system, that is approximately size T or U, and in the European system it falls around size 62 or 63. Men's ring sizes tend to have more variation than women's because hand size differences are more pronounced in the male population. Active men or those who work with their hands often have larger ring sizes due to muscle and knuckle size. The ring finger on the dominant hand is also typically slightly larger than on the non-dominant hand, so it matters which hand you measure if the ring is meant for a specific finger.
Yes, ring sizing systems differ significantly between countries, which is one of the main reasons conversion charts exist. The United States and Canada use a numerical system that runs from about size 3 to size 16, with half and quarter sizes available. The United Kingdom, Ireland, and Australia use an alphabetical system from A to Z, with half sizes. Continental Europe uses a numerical system based on the inner circumference in millimeters, so a European size 52 means the ring has an inner circumference of 52mm. Japan uses its own numerical system that starts at size 1 and goes up to about size 30. The underlying measurement is the same everywhere, but the labeling system changes. This converter handles the four most commonly used systems so you can shop internationally without confusion.
Yes, your finger size fluctuates throughout the day, and these fluctuations can be significant enough to affect ring fit. Fingers are typically at their smallest in the morning, especially if you sleep in a cool room. They tend to swell gradually during the day as you use your hands, with the largest size usually occurring in the late afternoon or evening. Temperature has a major effect as well. Cold weather causes blood vessels to constrict, making fingers noticeably thinner, while hot weather and exercise cause vasodilation and fluid retention that makes fingers swell. Other factors that cause temporary swelling include high salt intake, alcohol consumption, hormonal changes during menstrual cycles or pregnancy, and prolonged air travel. For the most representative measurement, jewelers recommend measuring in the afternoon.
If your measurement falls between two standard sizes, the general rule is to go up to the larger size rather than down. A ring that is slightly loose is more comfortable and safer than one that is too tight, because tight rings can restrict blood circulation and become difficult or painful to remove, especially if your finger swells. Many jewelers offer half sizes and even quarter sizes, so you may be able to find an exact fit rather than rounding. The width of the ring band also matters: wider bands fit more tightly than narrow bands because they cover more skin area, so you may go up a half size for a wide band compared to your measurement. Consider ordering a ring sizer set for about $10, which gives you exact sizing.
Most rings can be resized, but the extent depends on the material, design, and construction. Simple gold, platinum, and silver bands are the easiest to resize and can typically be adjusted up or down by 1 to 2 full sizes without problems. Going beyond 2 sizes may compromise the structural integrity of the ring or distort its shape. Rings with stones set all the way around (eternity bands) are much harder to resize because changing the circumference affects the stone settings. Tungsten and titanium rings cannot be resized at all because these metals are too hard to work with traditional jeweler's tools. The cost of resizing typically ranges from $30 to $100 for a simple band, and $50 to $150 or more for rings with settings. Getting your size right saves both money and time.
Online ring sizing methods can get you within half a size of your true size if done carefully, but they are not as accurate as being measured by a professional jeweler with a proper mandrel and gauge set. The string or paper method introduces several potential sources of error. If the paper stretches, if you wrap it too tightly or too loosely, or if you do not pass it over the knuckle properly, your measurement could be off. Screen-based ring sizers that ask you to place an existing ring on your monitor are limited by screen resolution, display scaling settings, and whether you have calibrated the on-screen size correctly. The printable ring sizer approach works reasonably well if you print at exactly 100% scale. For the best results with any home method, measure multiple times on different days and at different times of day.
Sources and References
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