Ring size by circumference or diameter
Wrap a strip of paper round the finger, measure the length, and type it here in millimetres, centimetres or inches. Or type the inside diameter of a ring you own.
54 mm round is ISO 54, US 6.75 and UK N.
| System | Size | Match |
|---|---|---|
| US and Canada | 6.75 | closest: −0.2 mm |
| UK and Australia | N | closest: −0.3 mm |
| ISO / Europe | 54 | exact |
| Switzerland, Italy, Spain | 14 | exact |
| Japan | 14 | closest: +0.5 mm |
| Hong Kong and China | 15 | closest: +0.3 mm |
| India | 14 | exact |
How to measure a circumference
Cut a strip of paper about a centimetre wide, wrap it round the base of the finger where the ring will sit and mark where the end meets the strip. Lay the strip flat and measure from the end to the mark with a ruler. That length is the circumference.
Use paper or string that does not stretch. Measure a few times and take the middle value, because the strip can be pulled tight or left slack.
Circumference in mm, cm and inches
| mm | cm | inches | ISO | US | UK |
|---|---|---|---|---|---|
| 44 | 4.4 | 1.73 | 44 | ≈ 3 | ≈ F |
| 45 | 4.5 | 1.77 | 45 | ≈ 3.25 | G |
| 46 | 4.6 | 1.81 | 46 | 3.75 | ≈ H |
| 47 | 4.7 | 1.85 | 47 | ≈ 4 | H½ |
| 48 | 4.8 | 1.89 | 48 | 4.5 | I½ |
| 49 | 4.9 | 1.93 | 49 | ≈ 5 | ≈ J |
| 50 | 5 | 1.97 | 50 | 5.25 | K |
| 51 | 5.1 | 2.01 | 51 | ≈ 5.75 | ≈ L |
| 52 | 5.2 | 2.05 | 52 | 6 | L½ |
| 53 | 5.3 | 2.09 | 53 | 6.5 | M½ |
| 54 | 5.4 | 2.13 | 54 | ≈ 6.75 | ≈ N |
| 55 | 5.5 | 2.17 | 55 | 7.25 | O |
| 56 | 5.6 | 2.2 | 56 | ≈ 7.5 | ≈ P |
| 57 | 5.7 | 2.24 | 57 | 8 | P½ |
| 58 | 5.8 | 2.28 | 58 | ≈ 8.5 | Q½ |
| 59 | 5.9 | 2.32 | 59 | 8.75 | ≈ R |
| 60 | 6 | 2.36 | 60 | ≈ 9.25 | S |
| 61 | 6.1 | 2.4 | 61 | ≈ 9.5 | ≈ T |
| 62 | 6.2 | 2.44 | 62 | 10 | T½ |
| 63 | 6.3 | 2.48 | 63 | ≈ 10.25 | U½ |
| 64 | 6.4 | 2.52 | 64 | 10.75 | ≈ V |
| 65 | 6.5 | 2.56 | 65 | ≈ 11.25 | W |
| 66 | 6.6 | 2.6 | 66 | 11.5 | ≈ X |
| 67 | 6.7 | 2.64 | 67 | ≈ 12 | X½ |
| 68 | 6.8 | 2.68 | 68 | ≈ 12.25 | Y½ |
| 69 | 6.9 | 2.72 | 69 | 12.75 | ≈ Z |
| 70 | 7 | 2.76 | 70 | ≈ 13 | Z+1 |
| 71 | 7.1 | 2.8 | 71 | 13.5 | ≈ Z+2 |
| 72 | 7.2 | 2.83 | 72 | ≈ 14 | Z+2½ |
| 73 | 7.3 | 2.87 | 73 | 14.25 | ≈ Z+3 |
| 74 | 7.4 | 2.91 | 74 | ≈ 14.75 | ≈ Z+3 |
Questions
What ring size is 6 cm?
A circumference of 6 cm is 60 mm, which is ISO 60 and about US 9.
How do I change a diameter into a circumference?
Multiply the inside diameter by 3.1416. A ring 17.3 mm across inside is 54.4 mm round, which is ISO 54.