How to Measure Your Ring Size

Method 1: measure a ring that already fits

The most accurate thing you can do without a sizer, and the only method that works for a surprise.

1. Pick the right ring. It has to be one worn on the same finger of the same hand as the new ring. A ring from the other hand will be about half a size out.
2. Measure the inside diameter. Lay the ring flat and measure straight across the inside, at the widest point, in millimetres. Measure the opening, not the metal.
3. Match it to a size. 16.5 mm is a US size 6; 18.9 mm is a US size 9. Use the reference table below, or the full conversion chart for every size and every country.
4. Allow for the band width. If the ring you measured is narrow and the one you are buying is 6 mm or wider, add half a size.

Method 2: measure your finger directly

Use this when there is no existing ring to work from. It is less precise than measuring a ring, so treat the result as a strong indication rather than a final answer.

1. Cut a thin strip of paper about 5 mm wide, or use a piece of non-stretchy string. Avoid anything elastic, it will read small.
2. Wrap it around the base of the finger, snug but not tight. It should sit the way a ring would, not pinch.
3. Mark where it overlaps with a pen, then unwrap it and lay it flat against a ruler.
4. Read the length in millimetres. That is your inside circumference, 51.8 mm is a US size 6, 62.1 mm is a US size 10.
5. Check the knuckle. Repeat the measurement over the knuckle. If it is much larger, choose a size between the two so the ring passes but still sits snug.

Quick size reference

The most commonly ordered sizes, with the measurements you will have taken above. For half and quarter sizes, and for UK, European and Asian equivalents, see the full ring size conversion chart.

If your measurement falls between two rows, take the larger size.

Tips for an accurate measurement

Finger size isn’t fixed; it shifts with temperature, time of day, and band width. A few habits make the difference between a good guess and a confident fit:

Need to convert between US, UK, and European sizes? See our international ring size conversion chart.

Frequently asked questions

How can I measure my ring size without a ring sizer?

The most reliable at-home method is measuring the inside diameter of a ring that already fits the intended finger, then matching that measurement to a size chart. String and paper-strip methods work but tend to stretch or overlap unevenly, so they often read small. If you can wait a few days, a free mailed sizer is considerably more accurate than either.

What if I am between two ring sizes?

Choose the larger of the two. A slightly loose ring is comfortable and easy to size down; a tight one cannot be worn at all. Go up rather than down especially if you have prominent knuckles or you are buying a wide band.

When is the best time to measure my ring size?

At the end of the day, at normal room temperature, when your fingers are at their typical size. Fingers run smaller in the morning and in cold weather and swell after exercise, salt, or heat. Measure two or three times across different days before settling on a size.

Do wide bands fit differently?

Yes. Bands 6 mm and wider cover more of the finger and fit more snugly, so most people need about half a size larger than their usual measurement. Whenever possible, size with a sizer in the same width as the band you intend to buy.

Are printable ring sizers accurate?

Only if you verify the scale. Printers and PDF viewers frequently resize a page by a few percent, which is easily half a ring size. If you use a printable sizer, print at 100% with no page scaling and check the printed ruler against a real one before trusting the result.

How do I find my partner's ring size for a surprise?

Borrow a ring they already wear on the correct finger and measure its inside diameter, or press it into a bar of soap to take an impression you can measure later. A close friend or family member often knows the size outright. If you have to guess, the most common sizes are US 6 to 7 for women and US 9 to 10 for men.

Does 25karats really send ring sizers for free?

Yes. We mail a reusable plastic ring sizer at no cost, with no purchase required, to addresses in the USA and Canada. It is the same tool we recommend to every customer before ordering.

Can my ring be resized later if I get it wrong?

Most plain and lightly set gold and platinum rings can be resized, and at 25karats most designs can be adjusted up or down one size free within 60 days. Eternity bands set with stones all the way around, and rings patterned around the full circumference, often cannot be resized at all, so those need the size right the first time.

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