Ring size conversion chart
Type a measurement and the sizes appear here.
Sizes are for guidance, following BS 6820 and ISO 8653 as checked on 2026-10-23. Brands cut sizes differently: try the ring on or ask your jeweller before you buy. Disclaimer
Know one size and need another? Pick the system you have, read across. Every row is computed from the definition of each system.
Ring size conversion chart, every system
Read down to your size in the column you know, then across. The two millimetre columns on the right are what a jeweller actually cuts to, so quote those if you are ordering from abroad.
| US / CA | UK / AU | EU / ISO | JP 号 | CN / HK | IN | IT / ES / CH | Diameter | Circumference |
|---|---|---|---|---|---|---|---|---|
| 3 | F½ | 44 | 4 | 6 | 4 | 4.2 | 14.1 | 44.2 |
| 3½ | G½ | 45 | 5 | 7 | 5 | 5.5 | 14.5 | 45.5 |
| 4 | H½ | 47 | 7 | 8 | 7 | 6.8 | 14.9 | 46.8 |
| 4½ | I½ | 48 | 8 | 9 | 8 | 8.0 | 15.3 | 48.0 |
| 5 | J½ | 49 | 9 | 11 | 9 | 9.3 | 15.7 | 49.3 |
| 5½ | K½ | 51 | 10 | 12 | 11 | 10.6 | 16.1 | 50.6 |
| 6 | L½ | 52 | 12 | 13 | 12 | 11.9 | 16.5 | 51.9 |
| 6½ | M½ | 53 | 13 | 14 | 13 | 13.1 | 16.9 | 53.1 |
| 7 | N½ | 54 | 14 | 15 | 14 | 14.4 | 17.3 | 54.4 |
| 7½ | O½ | 56 | 15 | 16 | 16 | 15.7 | 17.7 | 55.7 |
| 8 | P½ | 57 | 16 | 18 | 17 | 17.0 | 18.1 | 57.0 |
| 8½ | Q½ | 58 | 18 | 19 | 18 | 18.3 | 18.5 | 58.3 |
| 9 | R½ | 60 | 19 | 20 | 20 | 19.5 | 18.9 | 59.5 |
| 9½ | S½ | 61 | 20 | 21 | 21 | 20.8 | 19.4 | 60.8 |
| 10 | T½ | 62 | 21 | 22 | 22 | 22.1 | 19.8 | 62.1 |
| 10½ | U½ | 63 | 23 | 23 | 23 | 23.4 | 20.2 | 63.4 |
| 11 | V½ | 65 | 24 | 24 | 25 | 24.6 | 20.6 | 64.6 |
| 11½ | W½ | 66 | 25 | 26 | 26 | 25.9 | 21.0 | 65.9 |
| 12 | Y | 67 | 26 | 27 | 27 | 27.2 | 21.4 | 67.2 |
| 12½ | Z | 68 | 27 | 28 | 28 | 28.5 | 21.8 | 68.5 |
| 13 | Z+1 | 70 | 29 | 29 | 30 | 29.7 | 22.2 | 69.7 |
| 13½ | Z+2 | 71 | 30 | 30 | 31 | 31.0 | 22.6 | 71.0 |
Where these numbers come from
- United States, Canada and MexicoPublished standard
- Inside diameter = 0.458 in + 0.032 in per size (11.63 mm + 0.8128 mm). Quarter sizes exist; shops stock half sizes.
- UK, Ireland, Australia, New Zealand, South AfricaPublished standard
- BS 6820:1987 — one letter is 1.25 mm of circumference and size C is 40.0 mm. Printed charts from different jewellers differ by up to half a size.
- Europe (ISO 8653)Published standard
- ISO 8653:2016 — the size is the inside circumference in millimetres, to the nearest millimetre.
- Japan (号, JCS)Published standard
- 1号 is 13.00 mm across and every 号 adds one third of a millimetre. JIS numbers (41号, 42号…) are the circumference instead — a different scale.
- China and Hong Kong (港号)Trade chart, no national standard
- Jewellery trade convention, not a published standard: about 1.1 mm of circumference per size. Charts differ by a few tenths of a millimetre.
- IndiaTrade chart, no national standard
- India has no national ring size standard. This column is the circumference less 40 mm, rounded — the chart most Indian jewellers print. Ask yours which chart they cut to.
- Italy, Spain and Switzerland
- The inside circumference with 40 mm taken off, so size 14 is 54 mm.
- Inside diameter (mm)
- Measured straight across the inside of the band.
- Inside circumference (mm)
- The way round the inside of the band — diameter × π.
UK to US ring size
The two scales were never aligned, so the letters fall between the numbers. UK N½ is US 7; UK N, one half-letter down, is US 6¾ — not US 6½ and not US 7. British sizes come from BS 6820:1987, where one letter division is 1.25 mm of circumference and size C is 40.0 mm.
There is a second problem that nobody mentions: British charts disagree with each other. For the letter N, Beaverbrooks prints 53.8 mm, H. Samuel prints 53.16 mm and Bridebook prints 54.4 mm. That spread is more than half a size. The chart on this page follows the standard; if you are ordering from a particular shop, use theirs.
| UK | US | EU / ISO | Inside round (mm) |
|---|---|---|---|
| H½ | 4 | 47 | 46.8 |
| I½ | 4½ | 48 | 48.0 |
| J½ | 5 | 49 | 49.3 |
| K½ | 5½ | 51 | 50.6 |
| L½ | 6 | 52 | 51.9 |
| M½ | 6½ | 53 | 53.1 |
| N½ | 7 | 54 | 54.4 |
| O½ | 7½ | 56 | 55.7 |
| P½ | 8 | 57 | 57.0 |
| Q½ | 8½ | 58 | 58.3 |
| R½ | 9 | 60 | 59.5 |
| S½ | 9½ | 61 | 60.8 |
| T½ | 10 | 62 | 62.1 |
| U½ | 10½ | 63 | 63.4 |
| V½ | 11 | 65 | 64.6 |
EU and ISO sizes
This is the easy one. ISO 8653:2016 defines the size as the inside circumference in millimetres, rounded to the nearest millimetre. ISO 54 is a ring 54 mm round the inside. France, Germany, Austria, Poland, the Netherlands and Scandinavia use this number directly. Italy, Spain and Switzerland write the circumference minus 40, so the same ring is size 14 there.
Japanese 号 and the JIS trap
Japanese sizes are whole 号 only. 1号 is 13.00 mm across the inside and every 号 adds one third of a millimetre, so 14号 is 17.3 mm across — close to US 7 but not identical, because the two scales step by different amounts.
The trap: Japan also has a JIS notation that writes the circumference as the size, so the same ring is 13号 in the ordinary JCS scale and about 54号 in JIS. If a Japanese shop quotes you a number in the forties or fifties, it is a circumference, not a 号.
India, China and Hong Kong
These two columns are the ones to treat with care, and we would rather say so than pretend otherwise.
India has no national ring size standard. The column here is the circumference less 40 mm, rounded to a whole number, which is the chart most Indian jewellers print and which matches the widely copied international table. Some Indian charts run one size off it. Ask the jeweller which chart they cut to before you order.
China and Hong Kong use 港号, a trade convention rather than a published standard: about 1.1 mm of circumference per size. Different houses’ charts are a few tenths of a millimetre apart. Quote the millimetres as well as the number.
| EU / ISO | IT / ES / CH | Diameter | Circumference | US / CA | UK / AU | JP 号 | CN / HK | IN |
|---|---|---|---|---|---|---|---|---|
| 41 | 1 | 13.1 | 41.0 | 1¾ | D | 1 | 3 | 1 |
| 42 | 2 | 13.4 | 42.0 | 2¼ | D½ | 2 | 4 | 2 |
| 43 | 3 | 13.7 | 43.0 | 2½ | E½ | 3 | 5 | 3 |
| 44 | 4 | 14.0 | 44.0 | 3 | F | 4 | 6 | 4 |
| 45 | 5 | 14.3 | 45.0 | 3¼ | G | 5 | 7 | 5 |
| 46 | 6 | 14.6 | 46.0 | 3¾ | H | 6 | 8 | 6 |
| 47 | 7 | 15.0 | 47.0 | 4 | H½ | 7 | 8 | 7 |
| 48 | 8 | 15.3 | 48.0 | 4½ | I½ | 8 | 9 | 8 |
| 49 | 9 | 15.6 | 49.0 | 5 | J | 9 | 10 | 9 |
| 50 | 10 | 15.9 | 50.0 | 5¼ | K | 10 | 11 | 10 |
| 51 | 11 | 16.2 | 51.0 | 5¾ | L | 11 | 12 | 11 |
| 52 | 12 | 16.6 | 52.0 | 6 | L½ | 12 | 13 | 12 |
| 53 | 13 | 16.9 | 53.0 | 6½ | M½ | 13 | 14 | 13 |
| 54 | 14 | 17.2 | 54.0 | 6¾ | N | 14 | 15 | 14 |
| 55 | 15 | 17.5 | 55.0 | 7¼ | O | 15 | 16 | 15 |
| 56 | 16 | 17.8 | 56.0 | 7½ | P | 15 | 17 | 16 |
| 57 | 17 | 18.1 | 57.0 | 8 | P½ | 16 | 18 | 17 |
| 58 | 18 | 18.5 | 58.0 | 8½ | Q½ | 17 | 18 | 18 |
| 59 | 19 | 18.8 | 59.0 | 8¾ | R | 18 | 19 | 19 |
| 60 | 20 | 19.1 | 60.0 | 9¼ | S | 19 | 20 | 20 |
| 61 | 21 | 19.4 | 61.0 | 9½ | T | 20 | 21 | 21 |
| 62 | 22 | 19.7 | 62.0 | 10 | T½ | 21 | 22 | 22 |
| 63 | 23 | 20.1 | 63.0 | 10¼ | U½ | 22 | 23 | 23 |
| 64 | 24 | 20.4 | 64.0 | 10¾ | V | 23 | 24 | 24 |
| 65 | 25 | 20.7 | 65.0 | 11¼ | W | 24 | 25 | 25 |
| 66 | 26 | 21.0 | 66.0 | 11½ | X | 25 | 26 | 26 |
| 67 | 27 | 21.3 | 67.0 | 12 | X½ | 26 | 27 | 27 |
| 68 | 28 | 21.6 | 68.0 | 12¼ | Y½ | 27 | 28 | 28 |
| 69 | 29 | 22.0 | 69.0 | 12¾ | Z | 28 | 28 | 29 |
| 70 | 30 | 22.3 | 70.0 | 13 | Z+1 | 29 | 29 | 30 |
| 71 | 31 | 22.6 | 71.0 | 13½ | Z+2 | 30 | 30 | 31 |
| 72 | 32 | 22.9 | 72.0 | 14 | Z+2½ | 31 | 31 | 32 |
| 73 | 33 | 23.2 | 73.0 | 14¼ | Z+3½ | 32 | 32 | 33 |
| 74 | 34 | 23.6 | 74.0 | 14¾ | Z+4 | 33 | 33 | 34 |
| 75 | 35 | 23.9 | 75.0 | 15 | Z+5 | 34 | 34 | 35 |
| 76 | 36 | 24.2 | 76.0 | 15½ | Z+6 | 35 | 35 | 36 |
Where these numbers come from
- Europe (ISO 8653)Published standard
- ISO 8653:2016 — the size is the inside circumference in millimetres, to the nearest millimetre.
- Italy, Spain and Switzerland
- The inside circumference with 40 mm taken off, so size 14 is 54 mm.
- Inside diameter (mm)
- Measured straight across the inside of the band.
- Inside circumference (mm)
- The way round the inside of the band — diameter × π.
- United States, Canada and MexicoPublished standard
- Inside diameter = 0.458 in + 0.032 in per size (11.63 mm + 0.8128 mm). Quarter sizes exist; shops stock half sizes.
- UK, Ireland, Australia, New Zealand, South AfricaPublished standard
- BS 6820:1987 — one letter is 1.25 mm of circumference and size C is 40.0 mm. Printed charts from different jewellers differ by up to half a size.
- Japan (号, JCS)Published standard
- 1号 is 13.00 mm across and every 号 adds one third of a millimetre. JIS numbers (41号, 42号…) are the circumference instead — a different scale.
- China and Hong Kong (港号)Trade chart, no national standard
- Jewellery trade convention, not a published standard: about 1.1 mm of circumference per size. Charts differ by a few tenths of a millimetre.
- IndiaTrade chart, no national standard
- India has no national ring size standard. This column is the circumference less 40 mm, rounded — the chart most Indian jewellers print. Ask yours which chart they cut to.
Questions people ask
What is UK size N in US sizes?
UK N is US 6¾ — about 53.8 mm round the inside. It is not US 7; a whole UK letter is 1.25 mm of circumference and a whole US size is 2.55 mm, so the two scales drift against each other.
What is US size 7 in EU sizes?
EU/ISO 54, because ISO sizes are simply the inside circumference in millimetres and US 7 measures 54.4 mm round.
What is 13号 in US sizes?
13号 is 17.00 mm across the inside, which works out at US 6.6 — so it is quoted as US 6½ on most charts. Japanese sizes come in whole numbers only, so nothing lines up exactly.
Why do two charts give me different answers?
Because for some systems there is no single right answer. ISO, US, UK and Japanese sizes all have a written definition; Indian and Chinese sizes do not, and even British retailers print circumferences for the same letter that differ by half a size. Where that happens, this site follows the written standard and says so under the chart.
Which number should I give a jeweller abroad?
The inside circumference in millimetres. It is the one number every system is built on, and it cannot be misread as a different country’s scale.