Enter your bust and band measurements to estimate your bra size, with band and cup conversions across US, UK, EU, FR/BE/ES and AU/NZ sizing systems.
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Bust size is the loose circumference around the fullest part of the breasts. Band size is the firm circumference measured directly underneath the breasts.
| Size | FR/BE/ES | EU (EN 13402) | US & UK | AU & NZ |
|---|---|---|---|---|
| XXS | 75 | 60 | 28 | 6 |
| XS | 80 | 65 | 30 | 8 |
| S | 85 | 70 | 32 | 10 |
| M | 90 | 75 | 34 | 12 |
| L | 95 | 80 | 36 | 14 |
| XL | 100 | 85 | 38 | 16 |
| XXL | 105 | 90 | 40 | 18 |
| 3XL | 110 | 95 | 42 | 20 |
| 4XL | 115 | 100 | 44 | 22 |
| 5XL | 120 | 105 | 46 | 24 |
| Difference | US Cup | UK/AU Cup |
|---|---|---|
| < 1" | AA | AA |
| 1" | A | A |
| 2" | B | B |
| 3" | C | C |
| 4" | D | D |
| 5" | E/DD | DD |
| 6" | F/DDD | E |
| 7" | G/DDDD | F |
| 8" | H | FF |
| 9" | I | G |
| 10" | J | GG |
| 11" | K | H |
| 12" | L | HH |
| 13" | M | J |
| 14" | N | JJ |
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Bust size is the loose circumference measured around the chest at the fullest part of the breasts, standing straight with arms at your sides, while wearing a properly fitted (non-padded) bra. Band size is the firm circumference measured directly underneath the breasts, snug but not tight. For best accuracy, measure to the nearest ¼ inch or ½ centimeter.
Band size is your underbust measurement rounded to the nearest even number (in inches), matching the standard US/UK sizing scale of 28, 30, 32, 34 and so on. Cup size is based on the difference between your bust and band measurements: each full inch of difference corresponds to one cup size (0-1" is AA, 1" is A, 2" is B, 3" is C, and so on up through N). Sizing conventions vary by country, this calculator also converts your band size to the EU (EN 13402), French/Belgian/Spanish, and Australian/New Zealand systems.
Studies suggest a large share of women wear an incorrectly fitted bra, partly because band and cup measurements aren't standardized across countries or even between manufacturers, a 34B from one brand may not fit the same as a 34B from another. Treat this calculator's result as a solid starting point for trying on bras, not a guaranteed exact fit.
Say your band measurement is 29 inches and your bust measurement is 35 inches. The band size rounds to the nearest even number, 30. The difference is then measured from that rounded band, not your raw underbust number, so it's 35 − 30 = 5 inches, which maps to a US cup size of E/DD and a UK/AU cup size of DD (each full inch of difference steps up one cup letter, 1" is A, 2" is B, and so on). That gives an estimated size of 30E/DD in the US or 30DD in the UK/Australia, alongside matching EU and FR/BE/ES band conversions shown in the results.
Measuring the band over a padded, ill-fitting, or overly loose bra, this throws off both the band and bust readings, measure band snugly (but not tight) directly underneath the breasts, and bust at the fullest point wearing a properly fitted, non-padded bra.
Assuming a cup letter means the same thing across every brand or country, cup sizing is relative to band size and isn't standardized between manufacturers, treat the result as a starting point for trying on bras, not a guaranteed universal fit.
Confusing the US cup letter with the UK/Australian one at larger sizes, they diverge after the D cup (e.g. a 6" difference is F/DDD in the US but only E in the UK/Australia system), use the conversion this tool provides rather than assuming the letters match internationally.
In the US, a 5-inch bust-to-band difference is labeled DD by some brands and E by others, there's no single agreed standard. Both refer to the same size.
US and UK/Australia cup labeling diverges after the D cup, for example a 6" difference is F/DDD in the US but only E in the UK/Australia system. This calculator shows both so you can shop confidently in either system.
Measure while wearing a well-fitted, non-padded bra for the most accurate bust measurement. Measuring bare-chested can understate your usual fullest-point measurement.
This calculator's band size table covers 28 to 46 inches (XXS to 5XL), the most commonly stocked range. Measurements outside this range are clamped to the nearest end of the table.
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