The easiest way to find your ring size at home is to measure the inside diameter of a ring that already fits that finger, in millimeters, and match it to a size chart: 17.3 mm is a US 7, for example. If you have no ring, wrap a strip of paper or string around the base of the finger, mark where it overlaps, measure that length in millimeters and divide by 3.14 to get the diameter. For an eternity band or anything set with stones all the way around, have it confirmed in person.
How do you measure ring size at home with a ring?
- Pick a ring that fits the same finger comfortably (rings fit differently on each hand and finger).
- Lay it flat on a ruler and measure the inside edge to inside edge, straight across the center, in millimeters.
- Find the closest diameter in the chart below. If you land between two sizes, go up to the larger one.
How do you measure ring size with string or paper?
- Cut a thin strip of paper (string stretches, paper does not) and wrap it snugly around the base of the finger.
- Make sure it can still slide over the knuckle; a ring has to pass the knuckle to get on.
- Mark where the paper overlaps, lay it flat and measure to the mark in millimeters. That is the circumference.
- Divide by 3.14 to get the diameter, or use the circumference column below.
Measure two or three times and take the middle result. Printable sizers and phone apps only work if the print or screen scale is exact, so check them against a real ruler.
Ring size chart in mm and inches
| US / Canada | Inside diameter | Circumference | UK / AUS |
|---|---|---|---|
| 3 | 14.1 mm | 44.3 mm | F |
| 4 | 14.9 mm | 46.8 mm | H |
| 5 | 15.7 mm | 49.3 mm | J |
| 6 | 16.5 mm | 51.8 mm | L |
| 7 | 17.3 mm | 54.3 mm | N |
| 8 | 18.1 mm | 56.9 mm | P |
| 9 | 19.0 mm | 59.7 mm | R |
| 10 | 19.8 mm | 62.2 mm | T |
| 11 | 20.6 mm | 64.7 mm | V |
| 12 | 21.4 mm | 67.2 mm | X |
| 13 | 22.2 mm | 69.7 mm | Z |
Diameters and letter sizes are from the MIT RCHI ring size guide; circumference is the diameter multiplied by pi (3.14159). To convert millimeters to inches, divide by 25.4 (a US 7 is about 0.68 inches across). Charts from different makers can vary slightly, which is another reason to confirm the size in person for an expensive or hard-to-resize ring.
How do you find someone's ring size for a surprise?
Borrow a ring they wear on the ring finger (or measure it against the chart while they are out) and use the diameter method above. Note which finger it came from: a ring from the right hand may not match the left. If you are unsure, it is usually easier to size a plain or solitaire ring up or down after the proposal than to guess on an eternity band.
Can a ring be resized if the size is wrong?
Most can. At our showroom, a simple resize is often same-day or next-day: the band is cut, adjusted, re-soldered and polished until the seam disappears. Plain bands, solitaires and rings with stones only across the top are straightforward. Rings with pavé around the band take more care, and full eternity bands and some tension settings are limited or cannot be resized at all. GIA makes the same point about channel, pavé and tension settings in its guide to ring settings. See our ring resizing service for details, and our settings guide before choosing a style.
Get sized at our Paramus showroom
The most reliable size comes from a jeweler's sizing ring on your own finger. Stop by our showroom inside The Jewelry Center on Route 4, Monday to Saturday from 10:15 AM to 6:30 PM, or book a time. If you are choosing a band to go with an engagement ring, our wedding band guide covers fit and resizing limits; if you are ordering a custom piece, sizing is part of the final fitting in our custom design process.
