Bra Size Calculator & Converter

About the Bra Size Calculator & Converter

Find your bra size from two measurements — the underbust and the bust, in centimetres or inches — or convert a size you already wear into another country’s system. The calculator gives the European size by EN 13402, the standard behind EU sizes (70B, 75C), with the equivalents that brands’ conversion charts print for France, Belgium and Spain, Italy, the UK, the US, Australia and New Zealand, and Japan and Korea.

It also shows the size the British tape method gives (band equal to the underbust in inches), which often has a smaller band and a bigger cup letter than the charts, and your sister sizes — the band-and-cup pairs that hold about the same cup volume. Because brands cut differently, every equivalent is a starting point for trying on, not a guarantee.

Common uses

• Finding a first size to try before buying online, from a tape measure at home.
• Buying a bra from another country: a US size in a European shop, a French or Italian brand in the UK, a Japanese brand anywhere.
• Finding a sister size when a style runs tight or loose in the band.
• Reading the size charts of brands that use EU, UK or US letters.

How each system works

• EU / International (EN 13402): the band is the underbust rounded to the nearest 5 cm (68–72 cm → 70), and the cup comes from bust minus underbust in 2 cm steps: AA 10–12 cm, A 12–14, B 14–16, C 16–18, D 18–20, E 20–22, F 22–24, G 24–26, H 26–28, and so on without doubled letters.
• France, Belgium, Spain: EU cups, band 15 more (EU 70 = FR 85).
• Italy: EU cups, band numbers 1, 2, 3 … (often I, II, III), EU band ÷ 5 − 12 (EU 70 = 2).
• UK, US, Australia and New Zealand: bands in inches (Australian bands as dress sizes, UK 32 = AU 10) and one cup per inch. Charts pair UK/US 32 with EU 70. UK cups run A, B, C, D, DD, E, F, FF, G, GG, H …; US cups D, DD (= E), DDD (= F), DDDD (= G), H, I …
• Japan and Korea: bands as in the EU; cups in 2.5 cm steps from AA = 7.5 cm (A 10, B 12.5, C 15 …), so a Japanese letter is usually one ahead of the EU letter for the same difference.

The band and cup tables of these systems are collected in the Wikipedia article Bra size.

Two ways to measure in inches

Conversion charts pair EU 70 with UK and US 32 — the old habit of adding about 4 inches to the underbust. Many British brands now label the band by the underbust itself: a 28-inch ribcage wears a 28 band, and the cup is one letter per inch of bust over the band. For the same body that gives a smaller band and a bigger cup letter (70B on the EU chart is about 28DD measured this way, the sister size of 32C).

Neither is wrong; they describe bras cut in different ways. If the band of a chart size rides up at the back or the cups gape, try the size the tape method gives, and its sister sizes.

Sister sizes

A bra’s cup volume depends on both numbers: going one band up and one cup down keeps about the same cup, so 32D, 34C and 30DD are sister sizes. Use them when a style fits in the cups but not in the band — a looser band means going up a band and down a cup, a tighter band the other way round.

Limitations

• Only the EU size follows a standard (EN 13402); the other equivalents are the ones brands’ conversion charts usually print. Cups step by different amounts (2 cm, 1 inch, 2.5 cm), so large cup letters drift apart between systems.
• Brands cut and stretch bands differently and label cups in their own ways; always check the brand’s own chart and try bras on.
• Measurements depend on how tight the tape is: measure the underbust snugly and the bust loosely, standing straight.
• Very small or very large cup differences may be outside these charts; specialist brands go further.

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