How Brazilian ring sizes work
Brazilian ring sizes, called aro or tamanho, are based on the ring's inner circumference. Under the Brazilian standard ABNT NBR 16058, the aro number is the inner circumference in millimetres minus 40.
- A ring with a 52 mm inner circumference is aro 12.
- A ring with a 54 mm inner circumference is aro 14.
- A ring with a 60 mm inner circumference is aro 20.
This makes the Brazilian system easy to convert. The EU/ISO size is also the inner circumference in millimetres, so aro = EU size − 40. EU 54 is aro 14, and EU 60 is aro 20.
Brazilian ring size conversion chart
| Aro (Brazil) | Circumference (mm) | Diameter (mm) | US | UK | EU |
|---|---|---|---|---|---|
| 7 | 46.7 | 14.86 | 4 | H | 47 |
| 8 | 48.0 | 15.27 | 4½ | I | 48 |
| 9 | 49.3 | 15.70 | 5 | J½ | 49 |
| 11 | 50.6 | 16.10 | 5½ | K½ | 51 |
| 12 | 51.9 | 16.51 | 6 | L½ | 52 |
| 13 | 53.1 | 16.92 | 6½ | M½ | 53 |
| 14 | 54.4 | 17.35 | 7 | N½ | 54 |
| 16 | 55.7 | 17.75 | 7½ | O½ | 56 |
| 17 | 57.0 | 18.19 | 8 | P½ | 57 |
| 18 | 58.3 | 18.53 | 8½ | Q½ | 58 |
| 20 | 59.5 | 18.89 | 9 | R½ | 60 |
| 21 | 60.8 | 19.41 | 9½ | S½ | 61 |
| 22 | 62.1 | 19.84 | 10 | T½ | 62 |
| 23 | 63.4 | 20.20 | 10½ | U½ | 63 |
| 25 | 64.6 | 20.68 | 11 | V½ | 65 |
| 26 | 65.9 | 21.08 | 11½ | W½ | 66 |
| 27 | 67.2 | 21.49 | 12 | X½ | 67 |
Aro values are the circumference minus 40, rounded to the nearest whole size.
Typical Brazilian ring sizes
Brazilian jewellers report that most women's rings sold in Brazil fall between aro 11 and 17, and most men's between aro 18 and 26.
Buying alianças: which hand to measure
In Brazil, couples often wear their aliança on the right hand during the engagement and move it to the left hand after the wedding. Fingers on the dominant hand are often slightly larger, so measure the finger on the hand you will wear the ring on most. If the ring will move between hands, measure both and choose the larger size.
Alianças are often wide or comfort-fit bands. For bands of 6 mm or more, choose half a size to one full aro larger than your measurement for a thin ring.
How to measure your aro at home
- Wrap a thin strip of paper or non-stretchy string around the base of the finger, mark where it overlaps, and measure the length in millimetres. Subtract 40 to get your aro.
- Or measure the inner diameter of a ring that fits and find it in the chart above.
- Or use the Ring Sizer app to measure a ring on your phone screen.
Frequently asked questions
What is the Brazilian ring size system?
Brazil numbers rings by inner circumference: the aro is the circumference in millimetres minus 40, as defined by ABNT NBR 16058.
How do I convert aro to a US size?
Aro 12 is about US 6, aro 14 is about US 7, aro 17 is about US 8, and aro 20 is about US 9. See the chart above for every size.
How do I convert aro to an EU size?
Add 40. Aro 14 is EU 54, and aro 18 is EU 58.
What size is aro 16 in the US?
Aro 16 is a 56 mm circumference, which sits between US 7½ and US 8. For a comfortable fit choose US 7½, or US 8 for a wide band.
