Ring Size Chart
Match your ring’s inside diameter or your finger’s circumference to US, UK and EU ring sizes. Use the converter above for any size.
Ring size chart
| US / Canada | UK / Australia | Inside diameter | Diameter (in) | Circumference (EU / ISO) |
|---|---|---|---|---|
| 3 | F½ | 14.1 mm | 0.554″ | 44.2 mm |
| 3.5 | G½ | 14.5 mm | 0.57″ | 45.5 mm |
| 4 | H½ | 14.9 mm | 0.586″ | 46.8 mm |
| 4.5 | I½ | 15.3 mm | 0.602″ | 48 mm |
| 5 | J½ | 15.7 mm | 0.618″ | 49.3 mm |
| 5.5 | K½ | 16.1 mm | 0.634″ | 50.6 mm |
| 6 | L½ | 16.5 mm | 0.65″ | 51.9 mm |
| 6.5 | M½ | 16.9 mm | 0.666″ | 53.1 mm |
| 7 | N½ | 17.3 mm | 0.682″ | 54.4 mm |
| 7.5 | O½ | 17.7 mm | 0.698″ | 55.7 mm |
| 8 | P½ | 18.1 mm | 0.714″ | 57 mm |
| 8.5 | Q½ | 18.5 mm | 0.73″ | 58.2 mm |
| 9 | R½ | 18.9 mm | 0.746″ | 59.5 mm |
| 9.5 | S½ | 19.4 mm | 0.762″ | 60.8 mm |
| 10 | T½ | 19.8 mm | 0.778″ | 62.1 mm |
| 10.5 | U½ | 20.2 mm | 0.794″ | 63.3 mm |
| 11 | V½ | 20.6 mm | 0.81″ | 64.6 mm |
| 11.5 | W½ | 21 mm | 0.826″ | 65.9 mm |
| 12 | X½ | 21.4 mm | 0.842″ | 67.2 mm |
| 12.5 | Y½ | 21.8 mm | 0.858″ | 68.5 mm |
| 13 | Z½ | 22.2 mm | 0.874″ | 69.7 mm |
How to measure your ring size at home
- Measure a ring you already wear on the same finger: put it on a ruler and measure the inside diameter in millimetres, edge to edge. Find that diameter in the chart.
- Or measure your finger: wrap a strip of paper or string around the base of the finger, mark where it overlaps, and measure the length in millimetres. That is your circumference — find it in the last column.
- Measure at the end of the day when fingers are slightly larger, and measure 3–4 times for a consistent result.
The ring size converter converts between all systems for sizes between the rows above.
Getting the fit right
- Knuckles: if your knuckle is wider than the base of your finger, choose a size between the two measurements so the ring slides over the knuckle.
- Wide bands (over about 6 mm) feel tighter; many jewellers suggest going up a quarter or half size.
- Temperature: fingers shrink in the cold and swell in heat, so avoid measuring right after exercise or when cold.
- Dominant hand: fingers on your dominant hand are often slightly larger.
Paper and string can stretch or slip, so a jeweller’s ring sizer is the most accurate option for an expensive ring. Sizes in the UK and Australia use letters; Europe and ISO use the inside circumference in millimetres; Japan and some other countries use their own numbers.
Average ring sizes
The most common women’s ring sizes in the US are around 6 to 7, and men’s around 9 to 10, though hands vary widely. For a surprise gift, borrow a ring the person wears on the same finger and measure its inside diameter.
Notes
US sizes follow the standard scale: inside diameter ≈ 11.63 mm + 0.8128 mm × US size. Circumference (the EU / ISO size) = diameter × π. UK letters step by half a US size.
Frequently asked questions
What size is a 17 mm ring?
About US 6½–6¾ (UK M½–N).
What is US 7 in mm?
About 17.3 mm inside diameter, 54.4 mm circumference.
How do I find my ring size at home?
Measure the inside diameter of a ring that fits, or wrap paper around your finger and measure the circumference.
What is the average women’s ring size?
Around US 6 to 7.