Ordering a ring online without knowing your exact size is one of the most common (and most avoidable) reasons a piece ends up waiting for a resize. You do not need a jeweler to get a reliable measurement: with a strip of paper or a ring you already own, you can find your size in about five minutes. Here is how to do it accurately, plus a US size chart and a few rings to try once you know your number.
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A ring that is too loose can spin or slip off; one that is too tight is uncomfortable and hard to remove over the knuckle. Most rings can only be resized within a limited range, and eternity bands or channel-set rings, where stones wrap most of the way around, often cannot be resized much at all. An accurate measurement saves a trip to the jeweler.
Use paper rather than string when you can: string stretches slightly and gives a larger reading. Repeat two or three times and use the most consistent result.
If you own a ring that fits the intended finger comfortably, this is usually the most reliable method, because it is not affected by your finger swelling in the moment. Lay the ring flat, measure the inside diameter edge to edge in millimeters, and match it to the diameter column below.
Measure across the widest inside point, not at an angle. If the ring was worn on a different finger, use it only as a rough guide: sizes vary between fingers and hands (your dominant hand is often slightly larger).
| US size | Inside diameter | Inside circumference |
|---|---|---|
| 4 | 14.9 mm | 46.8 mm |
| 5 | 15.7 mm | 49.3 mm |
| 6 | 16.5 mm | 51.9 mm |
| 7 | 17.3 mm | 54.4 mm |
| 8 | 18.1 mm | 57.0 mm |
| 9 | 19.0 mm | 59.5 mm |
| 10 | 19.8 mm | 62.1 mm |
| 11 | 20.6 mm | 64.6 mm |
| 12 | 21.4 mm | 67.2 mm |
| 13 | 22.2 mm | 69.7 mm |
Each full US size adds about 0.8 mm of diameter (about 2.5 mm of circumference), so a half size is roughly 0.4 mm of diameter and a quarter size about 0.2 mm. Round to the nearest quarter or half size; if you are truly between two sizes, choose the larger.
Once you know your number, here are a few pieces available across a range of sizes:
IGI Certified Diamond Half-Eternity Band
18K white gold, channel-set diamonds. Sizes 5.5 to 10.
$9,149
Shop Now →
10K White Gold 3-Stone Engagement Ring
Brilliant and baguette clusters. Sizes 6.75 to 7.25.
$3,556
Shop Now →
Measuring the inside diameter of a ring that already fits the same finger is usually the most reliable. Combine it with the paper strip method for extra confidence.
Yes. Fingers swell in heat and after exercise and shrink in the cold. Measure in the evening at a comfortable temperature for the most typical fit.
Choose the larger size, especially for wide bands or if your knuckle is larger than the base of your finger. A jeweler can often add sizing beads or resize a plain band later.
One full US size is about 0.8 mm of inside diameter, or about 2.5 mm of circumference.
Yes. Weight changes, pregnancy, temperature and age can all change finger size, so remeasure if it has been a while.
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