Quick answer
The most accurate way to measure ring size at home is to measure the inside diameter of a ring that already fits the same finger and match it to the chart below. Without a ring, wrap a non-stretch paper strip around the finger, measure the circumference in millimeters, and convert. Measure late in the day with warm hands, check the knuckle, and if you land between sizes, go up.
Ring size is the detail that most often turns a good decision into a return. It is entirely measurable at home, provided you avoid the two mistakes almost everyone makes: measuring at the wrong time of day, and forgetting that the knuckle, not the base of the finger, decides whether a ring goes on.
What changes your ring size during the day?
Temperature. Fingers shrink in cold and swell in heat. A measurement taken with cold hands can read half a size small. Measure when your hands are warm and at rest.
Time of day. Fingers are typically at their largest in the late afternoon and evening, and smallest first thing in the morning. Late in the day is the more useful measurement, because that is when a ring is most likely to feel tight.
The knuckle. The ring has to pass the knuckle and then sit on the finger without spinning freely. If your knuckle is much larger than the base of your finger, size to the knuckle and accept a slightly looser fit below it.
How do you measure a ring you already own?
This is the most accurate method available at home, and the one to use if you can.
Take a ring already worn on the intended finger. Measure the inside diameter across the widest point with a ruler, in millimeters. Be precise: adjacent half sizes are only about 0.4 mm apart in diameter, so 0.2 mm is roughly a quarter size. Then find the closest match in the chart.
US ring size chart: diameter and circumference
| US size | Inside diameter (mm) | Inside circumference (mm) |
|---|---|---|
| 3 | 14.1 | 44.2 |
| 3.5 | 14.5 | 45.5 |
| 4 | 14.9 | 46.8 |
| 4.5 | 15.3 | 48.0 |
| 5 | 15.7 | 49.3 |
| 5.5 | 16.1 | 50.6 |
| 6 | 16.5 | 51.9 |
| 6.5 | 16.9 | 53.1 |
| 7 | 17.3 | 54.4 |
| 7.5 | 17.7 | 55.7 |
| 8 | 18.1 | 57.0 |
| 8.5 | 18.5 | 58.3 |
| 9 | 18.9 | 59.5 |
| 9.5 | 19.4 | 60.8 |
| 10 | 19.8 | 62.1 |
| 10.5 | 20.2 | 63.4 |
| 11 | 20.6 | 64.6 |
| 11.5 | 21.0 | 65.9 |
| 12 | 21.4 | 67.2 |
If your measurement lands between two sizes, go up rather than down.
How do you measure ring size with string or paper?
Use this when there is no existing ring to copy.
Cut a strip of paper about 6 mm wide, or take a length of non-stretch string. Wrap it around the base of the finger, snug but not tight, and mark where it overlaps. Take it off, lay it flat, and measure the length to your mark in millimeters. That is the circumference; use the right-hand column of the chart above. Adjacent half sizes differ by about 1.3 mm of circumference.
Then check that a loop of that length passes over the knuckle before you trust it. Avoid elastic, thread that stretches, or anything you have pulled tight. Every one of those reads small.
Is a ring sizer more accurate?
Yes. The most reliable option overall is a physical sizer, either a set of graduated metal rings or a plastic sizing gauge, because it measures the finger the way a ring actually sits, knuckle included. Inexpensive plastic sizers are widely available if you would rather do it privately, and a local jeweler can usually measure your finger in a few minutes.
IMPERVORA is an online-only store, so we cannot size you in person; one of the methods above, or a local jeweler, is the way to go.
How do you find a ring size for a surprise?
Borrow a ring your partner wears on the correct finger, ideally one they are not wearing that day, and measure it using the ring method above. Note which finger and hand it came from: sizes can differ between fingers and between hands, and the dominant hand is often slightly larger.
If borrowing is impossible, press one of their rings into a bar of soap or a piece of soft clay to take an impression, and measure the impression’s inside diameter. Treat that as an approximation, not a confirmed size.
Guessing from typical sizes is a poor substitute for measuring. If you genuinely cannot measure, choose a design that is offered in many sizes and check its resizing options with us before you order.
Does band width change the size you need?
Yes. A wide band covers more of the finger and feels tighter than a narrow one at the same nominal size. As a rule of thumb, for a band around 6 mm or wider, consider going up a half size. Comfort-fit bands, which are domed on the inside, slide over the knuckle more easily and can feel slightly roomier than a flat-inside band of the same size, so a measurement taken with a comfort-fit ring usually transfers well to another comfort-fit ring.
Can the ring be resized later?
Do not assume so. Whether a ring can be resized depends on its design. Plain metal bands are generally the simplest for a jeweler to resize. Eternity, channel-set and full pave designs frequently cannot be, because the stones run through the area a jeweler would need to cut, and some anniversary bands are made in a single size.
IMPERVORA does not list resizing as a service, so ask our Concierge about the specific design before ordering. If a ring arrives in the wrong size, an unworn ring in its original packaging can be returned within 30 days of delivery under our return policy (request a return authorization by email first; change-of-mind return shipping is paid by the customer). A ring that has been resized or altered by a third party cannot be accepted back, so decide before taking it to a jeweler.
Ring sizes at IMPERVORA
Every ring lists the sizes it is offered in on its product page, and you choose the size before adding it to your cart. Examples of the range:
- Platinum Comfort-Fit Half Round Wedding Band: sizes 4 to 12 including half sizes, comfort fit, in widths from 1 mm to 7 mm.
- 1 Carat Round Lab Grown IGI G/VS1 Diamond Solitaire Ring in 10K White Gold: sizes 3 to 9 in half sizes, on a 1.50 mm band.
- Round Cut Lab Grown Diamond Eternity Ring in 14k White Gold (2 cttw FG/VS2): an eternity design offered in sizes 4 to 9; with diamonds set around the band, get the size right at the point of order.
- Platinum 1/4 CTW Lab-Grown Diamond Anniversary Band, Round 1.5 mm Stones: listed in ring size 7 only, so confirm your size matches before ordering.
Frequently asked questions
What is the most accurate way to measure ring size at home?
Measure the inside diameter of a ring that already fits the same finger and match it to a size chart. A physical ring sizer is more reliable still; string and paper strips are the least precise.
Should I size up or down if I am between sizes?
Size up. A slightly loose ring can still be worn; a ring that will not pass the knuckle cannot. For bands about 6 mm or wider, consider a further half size up.
Does IMPERVORA offer ring resizing?
IMPERVORA does not list resizing as a service, and whether a ring can be resized depends on its design. Ask our Concierge before ordering. Unworn rings can be returned within 30 days of delivery.
Are my two hands the same ring size?
Not always. Sizes can differ between hands and between fingers, so measure the exact finger the ring will be worn on.
Next step
Once you have a size, browse engagement rings, wedding bands or rings for women. If you are unsure about the size or resizing options for a specific design, ask our Concierge before ordering; we reply within one business day. Choosing the ring itself? Start with how to choose an engagement ring, then 10K vs 14K vs 18K gold and platinum vs white gold for the metal.
Once you know the size, compare rings and bands on our bridal and anniversary jewelry page.
