Ring Size Guide: Measure at Home, Half Sizes and Free Resizing
Posted by YANIV SEGAL
To find your ring size at home, measure the inside diameter of a ring that fits, or wrap a strip of paper around your finger to get the circumference, then match the number to a US ring size chart. A US size 7 has an inside diameter of 17.3 mm and a circumference of 54.3 mm. Below is the full chart for sizes 4 to 13, two reliable measuring methods and what to do about half sizes.
Ring size chart: US sizes, diameter and circumference
Ring sizes measure the inside of the ring. Diameter is the distance straight across the inside; circumference is the distance around it, which equals your finger's measurement. Circumference here is diameter multiplied by 3.1416, rounded to one decimal.
| US ring size | Inside diameter | Inside circumference |
|---|---|---|
| 4 | 14.9 mm | 46.8 mm |
| 5 | 15.7 mm | 49.3 mm |
| 6 | 16.5 mm | 51.8 mm |
| 7 | 17.3 mm | 54.3 mm |
| 8 | 18.2 mm | 57.2 mm |
| 9 | 19.0 mm | 59.7 mm |
| 10 | 19.8 mm | 62.2 mm |
| 11 | 20.6 mm | 64.7 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, so a half size is roughly 0.4 mm. That small step is why half sizes matter: a ring that is half a size off can feel either loose or tight.
How to measure ring size at home
There are two dependable methods. Use both if you can and compare.
Method 1: measure a ring that already fits
- Choose a ring worn on the same finger. Fingers on the dominant hand are often slightly larger.
- Lay it on a ruler and measure the inside edge straight across the widest point, in millimeters.
- Do not include the metal itself; measure inside edge to inside edge.
- Match the number to the diameter column above. Between two sizes? Pick the larger, or the half size in between.
Method 2: measure your finger with paper or string
- Cut a thin strip of paper or use a non-stretch string.
- Wrap it around the base of the finger, snug but not tight.
- Mark where it overlaps, then lay it flat and measure the length in millimeters.
- Match the length to the circumference column. Then check that the size will pass over your knuckle.
- Repeat two or three times at different times of day and use the most common result.
Tips for an accurate ring size
- Measure at the end of the day. Fingers swell through the day and in warm weather, and shrink when cold.
- Mind the knuckle. If your knuckle is much larger than the base of the finger, size for the knuckle so the ring can go on, or choose the half size between.
- Wide bands fit tighter. A wide band or signet covers more skin and feels snugger than a thin band at the same size. Many people go up a half size for bands over about 6 mm wide.
- Don't measure after exercise or a hot shower. Your reading will be on the large side.
Half sizes: do you need one?
If your measurement falls between two whole sizes, yes. Half sizes exist because a 0.8 mm jump in diameter is noticeable on a finger. A ring that spins or slides toward the knuckle is a risk for the stone. A ring that leaves a deep mark is uncomfortable to wear every day.
Our replica comes in half sizes from 4 to 13, which makes it the most reliable way to confirm a half size before you buy.
Test the fit with a $199 replica
Paper and string get you close. Wearing the ring tells you for sure. The Try It In Real Life replica is a $199 replica of any ring design, in sizes 4 to 13 including half sizes. You keep it, and the full $199 is credited toward any order of $1,000 or more. The credit never expires.
The replica shows you size, width and how the stone sits on your hand at the same time, which is why it is the step we recommend most for proposals. On the product pages, the main photo also switches to the exact metal and stone variant you choose, so you know what you are buying before checkout.
What if the size is wrong? Free resizing
Every Segal ring includes free resizing within 60 days. If the ring arrives and feels too loose or too tight, we adjust it at no charge. Our lifetime warranty and 30-day returns cover you beyond that.
A note on proposals: if you are sizing secretly, borrowing a ring from the same finger is the safest method. Our guide to buying an engagement ring online has more ways to get it right.
Men's ring sizes
Men usually wear larger sizes and wider bands, which makes the width tip above even more important. Bands like the Wyatt No. 1 black titanium and gold ring (from $2,288) and the Aiden No. 1 diamond black ring (from $3,782) cover more of the finger than a slim band. If you are between sizes on a wide men's band, go up. Our men's engagement ring guide has more on sizing men's styles.
Shop the look
| Piece | Price | Why we picked it |
|---|---|---|
| Heart Shape Diamond Ring - Noelle No. 3 | from $5,400 | Heart center stone; the photo updates to your chosen metal and stone |
| Pear Shaped Halo Diamond Ring - Janet No. 5 | from $2,195 | Pear halo with a black center stone |
| Leaves All Around Ruby Ring - Sydney 2ct No. 26 | from $3,705 | Leaf-pattern band with a ruby center |
| Black Titanium & Gold Men's Ring - Wyatt No. 1 | from $2,288 | Wide men's band; size up if you are between sizes |
Frequently asked questions
What is the most common ring size? Sizes vary widely by person, so use your own measurement rather than an average. The chart above covers US sizes 4 to 13.
How do I convert millimeters to ring size? Measure the inside diameter of a ring that fits and match it to the chart. For example, 17.3 mm is a US size 7, and 19.0 mm is a size 9.
Should I size up or down if I'm between sizes? Size up, or choose the half size between. A slightly larger ring is safer for the stone and easier to adjust.
Is resizing free? Yes. Every Segal ring includes free resizing within 60 days, plus a lifetime warranty and 30-day returns.
Can I try a ring on before buying? Yes. The $199 Try It In Real Life replica comes in sizes 4 to 13 including half sizes, and the $199 is credited on orders of $1,000 or more.
