Free Ring Size Calculator
Find your perfect ring size in seconds. Measure at home using string or an existing ring, and get your size in US, UK, EU, and Japanese sizing systems. No signup required.
Definition and Scope
A ring size calculator is a measurement-based tool that converts finger circumference or ring diameter into standardized ring sizes used across different regions (US, UK, EU, Japan), helping you find the correct ring size for jewelry purchases.
Applies To
- ✓Finding your ring size for online jewelry purchases
- ✓Converting ring sizes between US, UK, EU, and Japanese systems
- ✓Measuring ring size at home using string, paper, or existing rings
- ✓Gift purchases when you need to secretly determine ring size
Does NOT Apply To
- ✗Sizing for rings with unusual shapes or very wide bands (may need adjustment)
- ✗Medical or therapeutic ring fittings
- ✗Temporary ring sizing (swollen fingers, pregnancy, etc.)
Edge Cases
- ⚠Finger size varies throughout the day and with temperature
- ⚠Dominant hand fingers are typically slightly larger
- ⚠Wide bands (over 6mm) may require going up a half size
Methodology
How Results Are Derived
- Accept measurement input (circumference or diameter)
- Convert measurement to millimeters if needed
- Match against standardized size chart data
- Return closest matching sizes in all regional systems
Assumptions Made
- •Measurements are taken accurately at the intended finger
- •The finger is at its typical size (not swollen or cold)
- •Standard ring band width is assumed (2-4mm)
Simplifications Applied
- •Uses rounded values from standard conversion charts
- •Does not account for ring band width variations
- •Assumes symmetric finger shape
Uncertainty Declaration
Results are approximations. Ring sizes can vary slightly between jewelers and manufacturers. When in doubt, size up rather than down, as rings can be resized more easily when too large.
Limitations and Known Issues
Failure Scenarios
- !Inaccurate measurements lead to incorrect size recommendations
- !Measuring with stretchy string gives inflated circumference
- !Measuring an ill-fitting existing ring
When Results May Mislead
- ⚠For rings with unusual band widths (consider sizing up for wide bands)
- ⚠When finger size fluctuates significantly (weight changes, pregnancy)
- ⚠For specialty rings that may use non-standard sizing
Version Notes
Conversion data based on current jewelry industry standards. Minor variations may exist between different jewelers.
External References
Ring size standards
ISO 8653:1986
Our conversion data aligns with international ring size standards
Jewelry sizing best practices
Gemological Institute of America
Our measurement guidelines follow professional jewelry industry practices
How to Measure Your Ring Size
Choose a measurement method
You can measure the circumference of your finger using string or paper, or measure the inside diameter of an existing ring that fits well.
Cut a strip of paper or string
For circumference method: Cut a thin strip of non-stretchy material about 10cm (4 inches) long. Paper from a sticky note works well.
Wrap around your finger
Wrap the strip snugly around the base of your finger where a ring would sit. It should be tight enough to not slip off but not uncomfortable.
Mark the overlap point
Use a pen to mark where the strip overlaps. For an existing ring, simply measure across the inside of the ring at its widest point.
Measure with a ruler
Use a ruler with millimeter markings to measure from the end of the strip to your mark. This gives you circumference. For rings, measure the inside diameter.
Enter into the calculator
Select whether you measured circumference or diameter, enter your measurement in mm or inches, and click Calculate to see your ring sizes.
Frequently Asked Questions
How do I find my ring size at home?
The easiest method is to wrap a thin strip of paper or string snugly around your finger, mark where it overlaps, and measure the length in millimeters. This is your circumference. Enter it into our calculator to get your ring size. Alternatively, measure the inside diameter of a ring that fits well.
What is the average ring size for women?
The average ring size for women is US 6 to 7, which corresponds to UK L-N, EU 52-54, or approximately 16.5-17.3mm diameter. However, ring sizes vary significantly between individuals, so measuring is always recommended.
What is the average ring size for men?
The average ring size for men is US 9 to 10, which corresponds to UK R-T, EU 59-62, or approximately 19-19.8mm diameter. Men typically have larger ring sizes than women due to larger hands.
How do I convert my US ring size to UK or EU?
Our calculator automatically converts between US, UK, EU, and Japanese sizes. For example, US 6 equals UK L-M, EU 51.5-52. The UK uses letters (A-Z), while EU uses the circumference in millimeters as the size number.
Should I size up or down if between sizes?
If you are between sizes, it is generally better to size up. A slightly larger ring is more comfortable and can be resized more easily than one that is too tight. This is especially true for wide band rings.
Does finger size change throughout the day?
Yes, fingers are typically largest in the evening and smallest in the morning. They also expand in heat and shrink in cold. For the most accurate size, measure at the end of the day when your body is at normal temperature.
How do I secretly find someone's ring size?
You can borrow a ring they wear on the correct finger and measure its inside diameter. Trace the inside of the ring on paper, press it into a bar of soap, or bring it to a jeweler. You can also ask their friends or family, or use a ring sizer while they sleep.
Is this ring size calculator free to use?
Yes, our ring size calculator is completely free with no signup required. Your measurements are processed locally in your browser and are never stored on our servers, ensuring complete privacy.
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