Most of the world measures in centimeters, but most bra size charts online are in inches. This page puts both side by side.
Step 1: the band from your underbust in cm
Measure snugly around the ribcage, just under the bust, keeping the tape level. Then find your band:
| Snug underbust | US / UK band | EU band | French band | AU band |
|---|---|---|---|---|
| 70–74 cm | 28 | 60 | 75 | 6 |
| 75–79 cm | 30 | 65 | 80 | 8 |
| 80–84 cm | 32 | 70 | 85 | 10 |
| 85–89 cm | 34 | 75 | 90 | 12 |
| 90–94 cm | 36 | 80 | 95 | 14 |
| 95–99 cm | 38 | 85 | 100 | 16 |
| 100–104 cm | 40 | 90 | 105 | 18 |
| 105–109 cm | 42 | 95 | 110 | 20 |
| 110–115 cm | 44 | 100 | 115 | 22 |
The European band is not your underbust number. An 85 cm underbust wears a 75, not an 85, because bra bands are made to stretch around the ribcage. Most European brands size this way, and it matches the US and UK system.
Step 2: the cup from the difference in cm
Measure loosely around the fullest part of the bust, then subtract the band measurement (the band from the table converted to cm, about 2.54 cm per inch). Each 2.5 cm or so is one cup:
| Bust minus band | UK | US | EU |
|---|---|---|---|
| 1 in (about 3 cm) | A | A | A |
| 2 in (about 5 cm) | B | B | B |
| 3 in (about 8 cm) | C | C | C |
| 4 in (about 10 cm) | D | D | D |
| 5 in (about 13 cm) | DD | DD | E |
| 6 in (about 15 cm) | E | DDD | F |
| 7 in (about 18 cm) | F | G | G |
| 8 in (about 20 cm) | FF | H | H |
| 9 in (about 23 cm) | G | I | I |
| 10 in (about 25 cm) | GG | J | J |
Up to D, every system uses the same letter. From DD the European letters run in single steps, so the US and UK DD is an EU E.
The EN 13402 chart, and why brands don’t follow it
There is a European standard, EN 13402, that defines bra sizes directly in centimeters. The band is your underbust rounded to 5 cm (73 to 77 cm is a 75), and each cup is a 2 cm step starting at 10 to 12 cm for AA.
On paper it is neat. In practice most brands don’t use it. Real bands stretch about 10 cm, so an underbust of 75 cm usually needs a smaller band than 75, and a cup scale that starts at 10 cm puts most people several letters too small. If a chart gives you a much bigger band and a much smaller cup than the tables above, it is probably following EN 13402. Trust the fit, and the brand’s own chart, over the standard.
Doing it the easy way
Switch the bra size calculator to cm, enter your underbust and bust, and it gives the size in every system, with sister sizes. No measuring tape? Print the printable tape, which has a centimeter scale, or use the ribbon method.
For converting a size you already know, see EU bra size conversion or the full bra size conversion chart.
Sources & method: sizing rules follow the standard band-and-cup system used by UK, US, AU and EU brands, checked against fitting guides from specialist retailers and fitting communities. How we work.