Fit & Sizing
Ring Size Guide
Everything you need to find the right fit, whether you are shopping for yourself or keeping a surprise.
How to Measure
Three Ways to Find Your Size
Visit Any Hamilton Store
The most accurate method. A specialist sizes your finger with a professional ring gauge, complimentary and without obligation, at any of our locations.
Measure a Ring You Own
Take a ring that fits the right finger well and measure the inside diameter in millimetres with a ruler, then find that measurement on the chart below.
Use a Strip of Paper
Wrap a narrow strip of paper snugly around the base of the finger, mark where it overlaps, and measure the length in millimetres against the circumference column.
Conversion Chart
International Ring Sizes
Find your measurement in the diameter or circumference column to read across to the US size we use on every product page.
| US & Canada | Inside diameter | Circumference | UK & Australia | Europe |
|---|---|---|---|---|
| 3 | 14.1 mm | 44.2 mm | F | 44 |
| 3.5 | 14.5 mm | 45.5 mm | G | 45.5 |
| 4 | 14.9 mm | 46.8 mm | H | 47 |
| 4.5 | 15.3 mm | 48.0 mm | I | 48 |
| 5 | 15.7 mm | 49.3 mm | J½ | 49 |
| 5.5 | 16.1 mm | 50.6 mm | K½ | 50.5 |
| 6 | 16.5 mm | 51.9 mm | L½ | 52 |
| 6.5 | 16.9 mm | 53.1 mm | M½ | 53 |
| 7 | 17.3 mm | 54.4 mm | N½ | 54.5 |
| 7.5 | 17.7 mm | 55.7 mm | O½ | 55.5 |
| 8 | 18.1 mm | 57.0 mm | P½ | 57 |
| 8.5 | 18.5 mm | 58.3 mm | Q½ | 58 |
| 9 | 19.0 mm | 59.5 mm | R½ | 59.5 |
| 9.5 | 19.4 mm | 60.8 mm | S½ | 61 |
| 10 | 19.8 mm | 62.1 mm | T½ | 62 |
| 10.5 | 20.2 mm | 63.4 mm | U½ | 63.5 |
| 11 | 20.6 mm | 64.6 mm | V½ | 64.5 |
| 11.5 | 21.0 mm | 65.9 mm | W½ | 66 |
| 12 | 21.4 mm | 67.2 mm | X½ | 67 |
| 12.5 | 21.8 mm | 68.5 mm | Z | 68.5 |
| 13 | 22.2 mm | 69.7 mm | Z+1 | 70 |
Sizes between those listed are available as quarter sizes. Measurements are rounded to the nearest tenth of a millimetre.
Fit Tips
Getting the Fit Right
A well-fitted ring passes over the knuckle with gentle resistance and sits at the base of the finger without spinning or pinching.
Measure at the end of the day, when fingers are at their largest, and avoid measuring when your hands are cold. If the knuckle is noticeably larger than the base of the finger, size to the knuckle and ask us about sizing beads, which keep the ring from turning.
Wide bands, eternity rings and rings with stones around the full circle fit more snugly and are harder to adjust later, so when in doubt, let us size you in person before you buy.
Ring Sizing FAQ
What if I am between two sizes?
Choose the larger of the two. A ring should slide over the knuckle with a little resistance and sit comfortably at the base of the finger without spinning.
Do wide bands fit differently?
Yes. Bands wider than about 6 mm cover more of the finger and feel tighter, so most people go up a half size from their usual measurement.
Can a ring be resized after purchase?
Most rings can be adjusted up or down by our bench jewelers. Eternity bands, rings with stones set all the way around, and some alternative metals such as tungsten cannot be resized, so sizing those correctly at the outset matters most. Ask your specialist about resizing for any piece you are considering.
How do I find someone else’s ring size for a surprise?
Borrow a ring they wear on the intended finger and measure its inside diameter against the chart, trace its inner circle on paper, or ask a friend or family member who may already know. If you are still unsure, choose a style that is easy to resize and we will adjust it after the proposal.
Which hand should I measure?
Measure the finger the ring will actually be worn on. The dominant hand is usually slightly larger, and fingers on the same hand can differ by a full size.
Does the time of day matter?
It does. Fingers are smallest first thing in the morning and when cold, and swell in heat, after exercise and at the end of the day. Measure in the late afternoon at a normal temperature for the most reliable reading.