International size guide: every category compared
Rings, shoes, hats, clothing and bras each use their own US, UK and EU numbering. See how the systems differ side by side, then jump to the full chart, converter or measuring guide for the category you need.
Five sizing categories, five different physical measurements. A ring size is built from a diameter in millimetres, a shoe size from a foot length in centimetres, a hat size from head circumference, a clothing size from chest or bust and waist, and a bra size from underbust and bust. None of the five scales share a formula, so a person's US size in one category tells you nothing about their US size in another.
The table below puts one example size from each category side by side using the exact data from that category's own chart. The quick-reference tables further down cover a wider band of common sizes, and every full chart, live converter and measuring guide is one link away.
Every category at a glance
| Category | Physical anchor | US example | UK example | EU example |
|---|---|---|---|---|
| Ring | Inside diameter (mm) | US 7 | UK N | EU 54 |
| Shoe | Foot length (cm) | US 8.5 (women) / 7 (men) | UK 6.5 | EU 40 |
| Hat | Head circumference (cm) | US 7 1/8 | UK 7 | EU 57 |
| Clothing (women's) | Bust (cm) | US 8 | UK 12 | EU 40 |
| Bra (band) | Underbust (cm) | US 34 | UK 34 | EU 75 |
These numbers are not interchangeable between categories. A US 8 means something different in every row above, because each category converts from its own physical measurement, not from a shared scale.
Ring size quick reference
Ring sizes are anchored to the inside diameter of the band in millimetres. This is a slice of common adult sizes; see the full ring size chart for every US, UK, EU and Japan size, or use the converter to check an exact measurement.
| US / Canada | UK / Australia | EU / ISO |
|---|---|---|
| 5 | J | 49 |
| 6 | L | 52 |
| 7 | N | 54 |
| 8 | P | 57 |
| 9 | R | 59 |
| 10 | T | 62 |
Full ring size chart and converter
Shoe size quick reference
Shoe sizes are anchored to foot length in centimetres, which is why they translate more reliably than a size number alone. This snapshot covers common EU sizes 36 to 46; see the full shoe size chart for the entire adult range plus kids, toddler and baby sizes.
| US Men | US Women | UK | EU | Foot length (cm) |
|---|---|---|---|---|
| 4 | 5.5 | 3.5 | 36 | 22.5 |
| 5.5 | 7 | 5 | 38 | 23.7 |
| 7 | 8.5 | 6.5 | 40 | 25 |
| 8.5 | 10 | 8 | 42 | 26.2 |
| 10 | 11.5 | 9.5 | 44 | 27.5 |
| 12 | 13.5 | 11.5 | 46 | 29.2 |
Full shoe size chart and converter
Hat size quick reference
Hat sizes come from head circumference. The letter sizes below map to the same US and UK fitted numbers used for baseball caps and fitted hats; see the full hat size chart for every half-size step and the fitted hat guide.
| Letter | US fitted | UK fitted | EU |
|---|---|---|---|
| XS | 6 5/8 | 6 1/2 | 53 |
| S | 6 7/8 | 6 3/4 | 55 |
| M | 7 1/8 | 7 | 57 |
| L | 7 3/8 | 7 1/4 | 59 |
| XL | 7 5/8 | 7 1/2 | 61 |
| XXL | 7 7/8 | 7 3/4 | 63 |
Full hat size chart and converter
Clothing size quick reference
Clothing is the least standardised system here, since brands set their own fit inside each band. The rows below use the standard women's bust measurement behind each letter size; see the full clothing size chart for men's, women's and youth sizing.
| Size | US | UK | EU |
|---|---|---|---|
| XS | 0 | 4 | 32 |
| S | 4 | 8 | 36 |
| M | 8 | 12 | 40 |
| L | 12 | 16 | 44 |
| XL | 16 | 20 | 48 |
| XXL | 20 | 24 | 52 |
Bra size quick reference
Bra band size comes from the underbust measurement; cup size is a separate calculation based on the difference between bust and band. See the full bra size chart and the bra size calculator to work out a complete size, not just the band.
| US / UK | EU (DE, NL) | FR / ES | Underbust (cm) |
|---|---|---|---|
| 32 | 70 | 85 | 68 to 72 |
| 34 | 75 | 90 | 73 to 77 |
| 36 | 80 | 95 | 78 to 82 |
| 38 | 85 | 100 | 83 to 87 |
Full bra size chart and calculator
International sizing questions
Do ring, shoe and clothing sizes use the same US size numbers?
No. Each category has its own scale tied to a different physical measurement, so the numbers are not comparable across categories. A US 8 ring (a diameter in millimetres), a US 8 shoe (a foot length in centimetres) and a US 8 dress (a bust and waist range) describe three unrelated things that only happen to share the digit 8.
Which sizing system travels best across countries?
The systems anchored to a metric physical measurement travel best: EU ring sizes are the inside circumference in millimetres, EU shoe sizes follow the Paris point in centimetres, and EU hat and clothing sizes key on centimetre measurements. US and UK numbers are historical scales, so they need a conversion table rather than a simple offset.
Why don't shoe, ring and hat sizes convert with the same formula?
Because each is anchored to a different body measurement: a ring to finger diameter, a shoe to foot length, a hat to head circumference, clothing to chest or bust and waist, and a bra to underbust and bust. The US to UK offset in one category has no bearing on the offset in another.
How is this comparison page sourced?
Every table above pulls directly from the same conversion data used on each category's own chart page, cross-checked against the published international sizing standards described on that page. Nothing on this page is estimated or invented for the comparison.
Last reviewed and updated on July 2, 2026. Every table on this page is pulled from the same data as its full category chart.