Ring Size Chart

What Is a Ring Size Chart?

If your finger circumference is 52 mm, your ring size is typically HK 12 or approximately US 6. A ring size chart aligns sizing standards used in different countries and regions, so you can convert between them without memorizing formulas. Common systems include Hong Kong sizing (widely used in Hong Kong and mainland China), US, EU/ISO, UK, and Japanese (JP) sizes. Hong Kong sizes are generally numbered from about 7 to 25; US sizes commonly run from 4 to 13; and EU sizes use finger circumference in millimeters—so EU 52 means a 52 mm circumference. Because the same finger measurement is labeled differently across standards, a conversion chart is essential when choosing a ring.

How to Use This Tool

Open our ring size chart to find an input area on the left and the full conversion table on the right. It is easy to use:
1. Enter your measurement in the “Finger Circumference (mm)” field, such as 52.
2. If you only know the diameter, switch to “Diameter (mm)” mode and enter that value instead.
3. Click “Convert,” or simply enter a value; the matching row in the table will be highlighted automatically.
4. The table displays the matching Hong Kong, US, EU, UK, and Japanese sizes, along with the suitable circumference range.
5. You can also browse the table in reverse: find the size you know, such as US 6, then view its equivalents in other systems.

Worked Example

Here is a practical example: Xiaoming wraps a thin piece of string around the base of his finger, marks where it overlaps, and measures the string with a ruler. It is 51.5 mm long. In our calculator, he:
1. Enters 51.5 in the “Finger Circumference” field.
2. Clicks “Convert.”
3. Sees the table jump to the 51.5 mm row: HK 11 (range 50.7–52.0 mm), US 5.5, EU 51.5, UK K½, and JP 10.
4. Checks the HK 11 guidance and sees that 51.5 mm sits in the middle of its 50.7–52.0 mm range, making it a standard fit. If he is buying from a US-sized brand, he can request US 5.5.

More Examples and Edge Cases

Consider a borderline measurement: Xiaohong measures her finger at 48.2 mm. In Hong Kong sizing, this is closer to HK 9 (47.8–49.0 mm) and near the boundary with HK 10 (49.0–50.7 mm). After entering 48.2, the table shows HK 9 and notes that it is close to a size boundary, so trying it on or measuring again is recommended. HK 9 may feel slightly tight for everyday wear; HK 10 may be a little loose but can be adjusted with a ring guard or sizing insert. Our chart also shows adjacent sizes to help you choose based on normal changes in finger size throughout the day. If you measure in winter, your fingers may be about 0.5–1 size smaller than in summer, so measure three times in a warm environment and use the average.

Common Use Cases

Choosing an engagement ring from afar: If you do not know your partner’s ring size and do not want to ask directly, discreetly borrow a ring they wear often. Measure its inside diameter with calipers, enter it in our chart, and get sizes in every standard. This helps you choose the correct US or EU size even when buying abroad.
Exchanging an online ring purchase: If a ring arrives too large or too small, customer service may ask for your Hong Kong size while you only have a previous circumference measurement. Enter the circumference into the calculator to find the equivalent size and arrange the exchange more easily.
Buying a ring for an older family member: They may say they used to wear “size 11,” while the brand now lists only US sizes. Find HK 11 in the table to see its US equivalent, around US 5.5–6, and order with confidence.

Common Mistakes to Avoid

1. Pulling the string too tight: If a thin string is not snug against the skin—or leaves an indentation—the measured circumference can be too small and the ring may fit too tightly. The string should rotate freely around the finger without slipping off.
2. Measuring only once: Finger size can vary by 0.5–1 size with temperature and time of day. Measure in the morning, afternoon, and evening, then use the average. If you fall between sizes, account for the season and expected fit.
3. Ignoring the knuckle: If your knuckle is noticeably wider than the base of your finger, use the knuckle circumference as the main reference; otherwise, the ring may not pass over it. Our tool lets you enter knuckle circumference and recommends a knuckle-first size.
4. Confusing regional size numbers: HK 12 is not US 12—US 12 corresponds to a circumference of about 67 mm, while HK 12 is only about 52 mm. Entering your circumference in the chart prevents this mix-up.
5. Measuring finger width with a ruler as the diameter: Fingers are not perfectly round, so estimating width by eye is inaccurate. Use a flexible tape to measure circumference, or use a professional ring mandrel.

Limitations and Notes

This chart is based on the general ISO 8653:2016 standard and common industry sizing practices in China. Individual jewelry brands may differ by ±0.2 mm because of manufacturing tolerances, so the actual ring fit should take priority. The tool is not suitable for non-round rings, such as square or irregular bands, or for extremely bony or significantly swollen fingers. If your finger circumference is below 40 mm or above 75 mm, it may fall outside common Hong Kong and US size ranges, and a custom ring may be the best option. The size mappings in this chart have been cross-checked, but we cannot be responsible for purchasing errors caused by measurement inaccuracies. Please confirm sizing with the brand’s customer service before buying.

Frequently Asked Questions

Where on my finger should I measure for a ring? Measure the base of the finger where you will wear the ring. If your knuckle is wider, measure the widest part of the knuckle as well so the ring can pass over it. Our tool lets you enter both measurements and uses the larger value for its recommendation.
How do I quickly convert Hong Kong sizes to US sizes? There is no need to memorize a formula. Enter your circumference into the calculator to see Hong Kong and US sizes together. As a rough guide, Hong Kong size is approximately US size × 2 + 8, but small differences exist between brands, so use the chart for the final conversion.
What ring size is a 50 mm finger circumference? A 50 mm circumference is around HK 10, US 5, and EU 50. This is generally a smaller ring size. If you are unsure, enter 50 to view every equivalent standard.
Is the EU size in this tool the same as finger circumference? Yes. EU sizing under the ISO standard is expressed directly in millimeters, so EU 52 means a finger circumference of 52 mm. It is the most straightforward system because no conversion is needed.
Why does my measurement differ from the jewelry store’s? Jewelry stores usually use standard ring sizers and mandrels. At-home measurements can vary based on string thickness, tension, and timing. Use your result as a reference, then confirm it with a professional tool in store.
Can I use this ring size chart offline? Once the page has loaded, the table is cached in your browser and can still be viewed and used offline. An internet connection is required the first time you open it.