US to AU conversion

30B in Australian Bra Size

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

Instant answer

30B (US) =

8B AU

In this sizing table, 30B in US sizing converts to 8B in Australian sizing.

Need an Australian calculator?

If you are starting from body measurements instead of a known label, use the AU/NZ calculator with centimetres selected by default.

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Not sure about your size? Recheck your measurements before comparing conversion labels.

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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 Australian sizing

Use 8B 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 Australian sizing

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

US sizes adjacent to 30B and their Australian equivalents.
US size	AU size	How it differs
32B	10B	One band step looser, same cup letter.
30A	8A	One cup step down, same band.
30C	8C	One cup step up, same band.

What this conversion means

A US 30B means a 30 band with a B cup step. The Australian equivalent in this table is 8B, which keeps the same general fit target but uses Australian labeling. If the cup feels close and the band feels off, sister sizing is usually the next thing to try.

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?

The useful way to read 30B is to separate the band from the cup step. 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?

Whether 30B feels small, average, or full depends on the body and on the brand. 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

30B can shift in feel from one retailer to another because brands grade bands and cups in their own way. 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

30B is easiest to compare when you try shapes that show both cup volume and band tension clearly. 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

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Comfort Band Co.

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Soft Cup Edit

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FAQ

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

Use 8B as the Australian 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 European sizing?

In this same table, 30B converts to 65B (EU). That helps when a retailer shows a European chart instead of a Australian 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.