Ring Size Converter

Convert ring sizes between US, UK, EU standards with inner circumference and diameter in millimeters.

Loading...
1. Select the ring sizing system you know - US (numeric), UK (letter), or EU (millimeter circumference). 2. Enter your known ring size in the selected system. 3. View the equivalent sizes in all three systems displayed side by side. 4. Check the inner circumference and diameter in millimeters for precise measurements. 5. Use the sizing tips to adjust for wide bands or temperature-related finger size changes.

About This Tool

Finding the right ring size is essential whether you are shopping for an engagement ring, wedding band, or fashion jewelry. Different countries use completely different ring sizing systems, and buying internationally or online requires accurate conversions. Our Ring Size Converter translates between US (numbered), UK (lettered), and EU (millimeter-based) ring sizing systems, and also displays the inner circumference and diameter in millimeters for each size.

The US system uses a numeric scale from roughly 3 to 15 with half-size increments. The UK and Australian system uses letters from A to Z. European sizes are based on the inner circumference in millimeters, which makes them the most precise. The converter shows all three systems side by side, plus the exact diameter, so you can match any size standard used by jewelers worldwide.

For the most accurate results, measure your ring size at the end of the day when your fingers are slightly larger, and avoid measuring when your hands are cold. Temperature, humidity, and even diet can cause your finger size to fluctuate by up to a full size. If you are between sizes, it is generally better to round up. For wide bands (6mm or more), go up an additional half size because wider rings fit more snugly.

Frequently Asked Questions

Wrap a thin strip of paper or string around the base of your finger, mark where it overlaps, and measure the length in millimeters. This gives you the circumference, which you can look up in the converter. Alternatively, measure the inner diameter of a ring that already fits well using a ruler, and enter that in millimeters.
The most common ring size for women in the US is between 6 and 7 (UK M to O, EU 52 to 55). For men, it is between 9 and 11 (UK S to V, EU 60 to 65). However, sizes vary widely based on individual hand size, finger shape, and which finger the ring is worn on.
The UK system assigns letters from A through Z to ring sizes, with each letter corresponding to a specific inner circumference. A is the smallest at about 37.8mm circumference, and Z is about 68.5mm. Half sizes exist between letters. This system is also used in Australia and several other Commonwealth countries.
Yes, significantly. Fingers swell in warm weather and shrink in cold weather. This can cause a difference of up to one full ring size. For the most accurate measurement, check your size at room temperature during the evening when fingers tend to be at their largest. Avoid measuring after exercise or when dehydrated.
Yes. Wide bands (typically 6mm or wider) feel tighter than narrow bands of the same diameter because more surface area contacts your finger. Most jewelers recommend going up by half a size for bands 6-8mm wide, and a full size for bands wider than 8mm. This ensures comfortable all-day wear.

Related Tools

Shoe Size Converter

Convert shoe sizes between US, UK, EU, and JP sizing systems for men, women, and children.

Cooking and Lifestyle

Clothing Size Converter

Convert clothing sizes between US, UK, EU, and Asian sizing for tops, bottoms, and dresses.

Cooking and Lifestyle

Length Converter

Convert between meters, feet, inches, centimeters, kilometers, miles, yards, and nautical miles instantly.

Unit Converters

Area Converter

Convert between square feet, square meters, acres, hectares, square kilometers, and square miles.

Unit Converters

Cooking Measurement Converter

Convert between cups, tablespoons, teaspoons, milliliters, grams, and ounces by ingredient density.

Cooking and Lifestyle