US to UK conversion

30B in UK Bra Size

Convert 30B from US sizing to UK sizing, with the full international table, nearby sister sizes, and fit checks in one place.

Instant answer

30B (US) =

30B UK

In this sizing table, 30B in US sizing converts to 30B in UK sizing.

Sizing varies by brand

A conversion gives you the closest label in another sizing system, but brands can grade cups, wires, and bands differently. Use the converted size as a starting point, then check the retailer's chart and the fit of the actual bra.

Before you buy in UK sizing

Use 30B as the translated label, not as a fit guarantee.
Check the retailer's size chart because some brands grade bands and cups differently.
If the cup volume feels close but the band changes, compare sister sizes before switching cup letters.
When possible, check return rules before buying across sizing systems.

Full conversion table for 30B

30B bra size conversion across US, UK, EU, French, and Australian sizing.
US	UK	EU	FR	AU
30B	30B	65B	80B	8B

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

Sizes near 30B in UK sizing

If 30B is close but not right, these are the neighbouring US sizes and what each one becomes in UK sizing. Band neighbours change the fit around the ribcage; cup neighbours change volume.

US sizes adjacent to 30B and their UK equivalents.
US size	UK size	How it differs
32B	32B	One band step looser, same cup letter.
30A	30A	One cup step down, same band.
30C	30C	One cup step up, same band.

What this conversion means

The 30 band is the base of 30B, and the B cup is converted through the UK cup sequence where needed. That gives 30B in UK sizing. Use the sister sizes below if the cup volume seems close but the band does not feel right.

Sister sizes for 30B

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

What measurements make a 30B?

30B starts with the underbust, then adds cup depth from the bust measurement. In the current calculator formula, the closest starting range is about 29-31 inches (74-79 cm) under the bust and about 31.5-32.5 inches (80-83 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.

Is 30B big or small?

The label 30B can look more dramatic than it fits, especially across systems. In this size set, the US equivalent uses a smaller 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 30B 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 30B differs between brands

Brand sizing matters for 30B because cup depth, wire width, and band stretch are design choices. 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 30B

A good shopping path for 30B starts with everyday support, then moves into outfit-specific shapes. 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

Placeholder for wire-free and lounge options.

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FAQ

Is 30B in the US the same as UK sizing?

Use 30B as the UK match for 30B in this dataset. The label may look similar in some systems, but it still belongs to a different sizing sequence.

What is 30B in French sizing?

In this same table, 30B converts to 80B (FR). That helps when a retailer shows a French chart instead of a UK one.

How do I know if 30B fits?

A good fit should feel secure without digging. Watch for a band that rides up, cups that wrinkle, or straps carrying most of the support.

What sister sizes work with 30B?

32A are the closest sister-size options for 30B 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?

Countries and brands do not all use the same band labels or cup-letter sequence. A conversion translates the closest standard label, but the final fit still depends on the specific bra.

What measurements usually make 30B?

The current calculator formula points to about 29-31 inches underbust and 31.5-32.5 inches bust, or roughly 74-79 cm and 80-83 cm. Treat that as a starting range and then check the real fit.