UK to US conversion

UK 34B in US Bra Size

Convert 34B from UK sizing to US sizing, with the full international table, sister sizes, and practical fit checks in one place.

Instant answer

34B (UK) =

34B US

In this sizing table, 34B in UK sizing converts to 34B in US sizing.

Full conversion table for 34B (US 34B)

34B bra size conversion across US, UK, EU, French, and Australian sizing.
US	UK	EU	FR	AU
34B	34B	75B	90B	12B

Bra sizing varies between brands. Use this as an accurate starting point and check the fit.

What this conversion means

34B is the UK label in this dataset, and it points back to 34B in US sizing. The band number may change a lot between systems, especially for EU and French labels, but the table keeps the intended fit target together.

Sister sizes for the US equivalent (34B)

Sister sizes: 32C and 36A can be worth checking when the cup volume feels close but the band needs a different feel.

What measurements make a 34B?

34B is built from a band measurement and a bust measurement, not from the label alone. In the current calculator formula, the closest starting range is about 33-35 inches (84-89 cm) under the bust and about 35.5-36.5 inches (90-93 cm) around the fullest part of the bust. The band comes from the underbust rounding, while the cup step comes from the difference between bust and band. This page uses 34B as the US equivalent for those measurement notes.

Is 34B big or small?

34B is not automatically big or small; it depends on the band and the cup together. In this size set, the US equivalent uses a middle band and a lower cup step. Cup letters are relative to the band, so a D on one band is not the same volume as a D on every other band. The most useful question is whether the band stays level and the cups hold smoothly, not whether the label sounds large or small.

If 34B doesn't fit right

Band rides up: The band may be too loose or stretched out; try a snugger band or compare the snugger sister size.

Cups gape: The cup may be too roomy, too deep, or pulled away by a loose band; check the band before changing cup volume.

Cups spill: The cup volume may be too small or the cup shape may be too closed; try one cup step up before changing the band.

Straps dig in: The straps may be compensating for a band that is not supporting enough; reset the band fit before tightening straps.

How 34B differs between brands

Two brands can print 34B or its equivalent on the tag and still cut the bra differently. A firmer elastic can make the same band feel smaller, and a shallow or narrow cup can make the same cup letter feel different. Check the retailer chart, read fit notes when available, and compare the label against the brand and region sizing guide before treating the conversion as final.

Shopping for 34B

When shopping for 34B, start with styles that make the band easy to judge. If the cup is in a lower or middle step, lightly lined T-shirt styles can make gaps easy to spot. Fuller cup steps often benefit from styles with steadier side support, deeper cups, or a balconette shape depending on breast shape. For special outfits, compare the fit needs in the outfit guides before choosing a strapless, plunge, or backless option.

Bras in your size

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Everyday Fit Store

Placeholder for a broad size range and return-friendly basics.

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Comfort Band Co.

Placeholder for supportive everyday styles by band and cup.

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Soft Cup Edit

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FAQ

Is 34B the same as 34B in the US?

In this dataset, 34B (UK) converts to 34B in US sizing. Some brands publish their own charts, so use this as the closest standard label and still check the real fit.

What is 34B in Australian sizing?

34B (UK) matches the same base record as 12B (AU). The full table on this page shows each supported label side by side.

How do I check the fit of 34B?

A good US fit should feel secure without digging. If 34B feels close in the cup but wrong in the band, compare the sister sizes before changing cup volume.

What sister sizes work with 34B?

32C and 36A are the closest sister-size options for 34B in this dataset. Try a sister size when cup volume feels close but the band needs to feel snugger or looser.

Why do bra sizes differ between countries?

Bra labels are written differently across US, UK, EU, French, and Australian systems. Cup letters can also diverge after D, so a converted label is a starting point rather than a promise of identical fit.

What measurements usually make 34B?

34B maps to US 34B here. The current calculator formula points to about 33-35 inches underbust and 35.5-36.5 inches bust, or roughly 84-89 cm and 90-93 cm. Treat that as a starting range and then check the real fit.