Get the ring size
You can't ask, and guessing wrong means the ring spins or stops at the knuckle while everyone watches. Four methods, best first.
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Method 1 · most accurate
Borrow a ring they already wear
It has to be one they wear on the ring finger, ideally the left hand. Take it to any jeweler for a 30-second sizing, or press it into a bar of soap and bring the impression. No time? Slide it down a tapered candle, mark where it stops, and measure that later.
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Method 2 · nearly as good
Trace it
Put the ring on paper and trace the inside of the circle a few times. Measure the inner diameter in millimeters and match it to the chart below.
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Method 3 · outsource it
Send the accomplice
A friend suggests trying on rings "for fun" at a mall or market and reports back. It works better than it has any right to.
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Method 4 · the educated guess
Go by averages, then size up
The most common women's ring size in the US is around 6, with most falling between 5 and 7. Men average around 10. If you're guessing, go slightly large. A loose ring still goes on.
Diameter to US size
Measure the inside of the ring, edge to edge, in millimeters.
| Inside diameter | US size | Inside diameter | US size |
|---|---|---|---|
| 14.9 mm | 4 | 17.3 mm | 7 |
| 15.3 mm | 4.5 | 17.7 mm | 7.5 |
| 15.7 mm | 5 | 18.1 mm | 8 |
| 16.1 mm | 5.5 | 18.5 mm | 8.5 |
| 16.5 mm | 6 | 18.9 mm | 9 |
| 16.9 mm | 6.5 | 19.8 mm | 10 |
The dominant hand runs bigger
A ring from their right hand is usually about half a size larger than the left ring finger needs, if they're right-handed. Adjust down a touch.
Wrong is fixable
Most plain bands resize up or down one to two sizes, and many sellers do the first resize free. Close is good enough.
Except for these
Eternity bands with stones all the way around, and some tension or heavily patterned settings, can't be resized much. If you're guessing the size, avoid them.