How to find your ring size at home
To find your ring size at home, wrap a thin paper strip around the base of the finger in the evening, mark where it overlaps, measure that length in mm and divide by 3.14 to get the inside diameter. Then match it to the chart below. If you own a ring that fits the same finger, measuring its inside diameter is more reliable. Best of all is a metal ring sizer set, which costs under $5 on Amazon, or a jeweler's sizing set, because every ring we sell is made to your size and we do not resize.
- One half size is only 0.4 mm of inside diameter.
- US 7 is 17.3 mm across the inside.
- Measure late in the day, with warm hands.
- Wide bands fit tighter than thin ones.
- We make women's and unisex US 4 to 10, men's US 7 to 13.
Three ways to measure, from best to worst
A US half size changes the inside diameter by about 0.4 mm and the inside circumference (the distance around) by about 1.3 mm. That is thinner than a pencil line on a ruler. It is why a careless home measurement can be off by a half size or more.
| Method | What you need | Typical error | Use it when |
|---|---|---|---|
| Jeweler's sizing set | A visit to any jeweler, or a metal ring sizer set (under $5 on Amazon) | Smallest; you feel the real fit over the knuckle | You can get to a store or order a sizer |
| A ring that already fits | The ring, a mm ruler or calipers | A ruler read 0.5 mm off is more than a half size; calipers are close | The ring fits the same finger on the same hand |
| Paper strip or string | Paper, pen, mm ruler | String stretches and paper curls; 1 to 2 mm off around the finger is about a half to full size | Nothing else is available |
The paper strip method, step by step
- Cut a strip of paper about 15 cm long and 5 mm wide. Paper beats string because it does not stretch (GIA notes string can stretch and paper can curl in humidity).
- Wrap it snugly around the base of the finger. Snug means it slides over the knuckle with a little push.
- Mark where the end overlaps. Measure from the end to the mark in mm.
- Divide by 3.14. That is the inside diameter. Find the nearest row in the chart.
- Repeat three times on different days, in the evening. Use the size that comes up most.
Measuring a ring that already fits
Lay the ring on a mm ruler and measure straight across the inside, edge to edge, at the widest point. Do not include the metal. Digital calipers from a hardware store read to 0.1 mm and remove most of the guesswork. Use a round, thin band if you have one: a chunky or oddly shaped ring gives a misleading number.
US ring size chart in mm
Inside diameter uses the formula 11.63 + 0.8128 x US size, the same numbers our ring size picker uses. Circumference is 3.1416 x diameter. The ISO column is the European system: ISO 8653 names a ring size by its inside circumference in mm, so a 54 is a ring 54 mm around the inside.
| US size | Inside diameter (mm) | Inside circumference (mm) | ISO / EU size | We make it in |
|---|---|---|---|---|
| 3 | 14.1 | 44.2 | 44 | Not offered |
| 3.5 | 14.5 | 45.5 | 45 | Not offered |
| 4 | 14.9 | 46.8 | 47 | Women's and unisex |
| 4.5 | 15.3 | 48.0 | 48 | Women's and unisex |
| 5 | 15.7 | 49.3 | 49 | Women's and unisex |
| 5.5 | 16.1 | 50.6 | 51 | Women's and unisex |
| 6 | 16.5 | 51.9 | 52 | Women's and unisex |
| 6.5 | 16.9 | 53.1 | 53 | Women's and unisex |
| 7 | 17.3 | 54.4 | 54 | Women's, unisex and men's |
| 7.5 | 17.7 | 55.7 | 56 | Women's, unisex and men's |
| 8 | 18.1 | 57.0 | 57 | Women's, unisex and men's |
| 8.5 | 18.5 | 58.2 | 58 | Women's, unisex and men's |
| 9 | 18.9 | 59.5 | 60 | Women's, unisex and men's |
| 9.5 | 19.4 | 60.8 | 61 | Women's, unisex and men's |
| 10 | 19.8 | 62.1 | 62 | Women's, unisex and men's |
| 10.5 | 20.2 | 63.3 | 63 | Men's |
| 11 | 20.6 | 64.6 | 65 | Men's |
| 11.5 | 21.0 | 65.9 | 66 | Men's |
| 12 | 21.4 | 67.2 | 67 | Men's |
| 12.5 | 21.8 | 68.5 | 68 | Men's |
| 13 | 22.2 | 69.7 | 70 | Men's |
We left UK letter sizes out. The conversion tables we checked disagreed with each other, and a wrong letter is worse than none. If you know your UK size, ask a jeweler to convert it with a physical sizer.
Fit rules that decide between two sizes
Heat, cold and time of day
Fingers shrink in the cold and swell in the heat, and a reading on a cool morning can differ from one taken on a warm afternoon (GIA). Measure in the evening at room temperature, not right after a workout, a hot shower or a walk in winter.
The knuckle rule
If your knuckle is bigger than the base of your finger, a ring sized for the base may not go on. GIA's warning is simple: measure only where the ring sits and it might not pass the joint. Measure both spots and choose a size in between.
Wide bands fit tighter
A wider band covers more skin, so it feels tighter at the same size. GIA says wide shanks usually need to be a bit larger. For bands over 4 mm, consider going up a half size. Thin solitaires and stacking bands need no adjustment.
Between two sizes
Go up. A slightly loose ring can be snugged by a local jeweler with a sizing insert or beads. A ring that will not pass your knuckle can't be worn at all.
How to find her ring size without asking
For a surprise proposal, these work, in order of how much we trust them:
- Borrow a ring she wears on her left ring finger. Take it to a jeweler to be sized, or measure the inside with calipers, then put it back. A ring from another finger or the other hand will not match.
- Press the ring into a bar of soap or trace the inside on paper if you can't take it out of the house (GIA suggests the soap impression). Measure the inside of the impression.
- Ask a close friend or family member to find out, for example by trying rings on together.
Sizes we make
Women's and unisex rings come in US 4 to 10 in half sizes. Men's rings come in US 7 to 13 in half sizes. Every ring is made to order in your size, stone and metal, and is at your door within 30 days. Sterling silver and in-stock pieces can be returned unworn within 30 days of delivery, with no restocking fee. 14K gold and platinum pieces made to order, engraved and custom pieces cannot be returned. Pick your size, then read how to choose an engagement ring or browse men's rings.
Questions people ask
How can I measure my ring size without a ring sizer?
Wrap a thin paper strip around the base of your finger, mark the overlap, measure it in mm and divide by 3.14. Match that diameter to the chart. Repeat on a few evenings, because a 1 mm slip is about a half size.
Should I size up or down if I am between sizes?
Size up. A slightly loose ring can be fitted with a sizing insert by a local jeweler, but a ring that will not pass your knuckle can't be worn. For bands wider than about 4 mm, going up a half size is common advice.
Can Azov Diamonds resize my ring later?
No. We do not resize any ring, because each piece is made overseas and a resize would mean shipping it abroad and back. Measure carefully before you order; a metal ring sizer set costs under $5 on Amazon. Sterling silver and in-stock rings can be returned unworn within 30 days of delivery; 14K gold and platinum rings made to order cannot. After 30 days, we can still arrange a repair or a re-plating for you. We quote the cost first, you pay what it costs us, plus shipping both ways.
Are EU ring sizes the same as circumference in mm?
Yes. The ISO 8653 standard used across most of Europe names a ring by its inside circumference in mm, so size 54 is 54 mm around, about a US 7.
Is my ring size the same on both hands?
Not always. Measure the exact finger the ring will go on, and borrow a ring from that same finger if you are sizing in secret.
Sources
- GIA 4Cs: How to Determine Ring Size, Tips and Ring Size Chart, checked 2026-09-28.
- ISO 8653:2016 Jewellery, Ring-sizes: Definition, measurement and designation, checked 2026-09-28.