Ring Size Converter
Convert ring sizes between US, UK, EU, and millimeter diameter.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Ring Size Converter
Converting between ring sizing systems is straightforward with this tool:
- Choose your input system. Select US if you know your US ring size number, Diameter (mm) if you have measured your finger or an existing ring, or EU if you have the circumference in millimeters.
- Enter your value. Type the size or measurement. The calculator converts to all other systems instantly.
- Use the results. The breakdown shows your US, UK (letter system), EU (circumference), and diameter in millimeters.
The most accurate way to measure your ring size is to measure the internal diameter of a ring that fits well using a ruler or calipers, then enter that mm value into the diameter field.
About Ring Sizing
Ring sizing systems differ significantly between countries. The US uses numbers from 0 to 16 in half-size increments. The UK uses alphabet letters starting at A. European sizing uses the internal circumference in millimeters. A US size 7 corresponds to a diameter of approximately 17.3 mm, a circumference of roughly 54.4 mm, and a UK size L.
Ring sizes can vary slightly between jewelers and manufacturers. A size 7 from one brand may fit differently than a 7 from another. For important purchases like engagement rings, professional sizing with a jeweler's mandrel or sizing ring set gives the most accurate result.
Frequently Asked Questions
How do I measure my ring size at home?
The easiest method is to measure an existing ring that fits well. Place it on a ruler and measure the internal diameter in millimeters, then enter that value into this converter. Alternatively, wrap a strip of paper around your finger, mark where it overlaps, measure the length in mm (this is your circumference), then use the EU circumference field. Measure in the evening when fingers are slightly larger, as fingers swell throughout the day.
What is the most common ring size for women?
The average ring size for women in the US is approximately size 6 to 7, corresponding to a finger diameter of about 16.5 to 17.3 mm. The ring finger on the left hand is typically the same size or slightly smaller than the right ring finger. Size 6 (16.5 mm diameter) is the most commonly ordered size for women's rings in North America.
What is the most common ring size for men?
The average ring size for men in the US is approximately size 9 to 10, corresponding to a diameter of about 18.9 to 19.8 mm. Men's ring fingers tend to be wider than women's, and ring size varies considerably with hand size and body type. Men typically wear their ring on the left ring finger for wedding bands.
What does EU ring size mean?
EU ring sizes represent the internal circumference of the ring in millimeters. For example, an EU size 54 means the inside of the ring has a circumference of 54 mm. This corresponds to a diameter of about 17.2 mm (circumference divided by pi) and a US size 7. EU sizing is used in most of continental Europe and is considered one of the most precise systems because it directly measures the ring opening.