Australian Bra Size Calculator & Converter
Convert your AU bra size (8, 10, 12, 14…) to US, UK, EU, FR & IT in seconds. Get your exact size, sister sizes & fit diagnosis — based on underbust cm, the true universal measurement.
How to measure correctly
- Wear a non-padded bra or no bra for accurate readings.
- Underbust: wrap tape snugly around your ribcage directly under the bust. Keep tape parallel to the floor. Exhale fully and measure.
- Overbust: measure around the fullest part of your bust. Tape should be loose enough to slide a finger underneath.
- Stand naturally — don’t lift arms or lean forward. Both measurements should be taken in the same posture.
- Round to the nearest 0.5 cm (or ¼ inch) for best accuracy.
International Size Conversions
Your Sister Sizes (Same Cup Volume)
Recommended Bras in Your Size
Hand-picked styles that ship to Australia, verified fit reviews from AU customers.
Measure correctly to get your accurate Australian bra size
What Is the Australian Bra Sizing System?
Australian bra sizing uses dress-style band numbers (8, 10, 12, 14, 16…) paired with UK cup letters (A, B, C, D, DD, E, F, FF, G). Band size is derived from your underbust measurement in centimetres — AU 10 equals 70 cm, AU 12 equals 75 cm, AU 14 equals 80 cm. Cup size is the difference between your overbust and underbust, with each cup letter representing roughly 2.5 cm of volume.
Unlike the US system — which uses inch-based band numbers like 32, 34, 36 — Australia inherited its band numbering from its clothing dress-size tradition. An AU 12 bra corresponds to someone who typically wears a size 12 dress. This makes Australian sizing intuitive for local shoppers, but creates confusion when buying from international retailers who use entirely different numbering conventions.
The cup letter system, however, is borrowed from the United Kingdom. Australia uses the extended UK lettering sequence: A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K. This is meaningfully different from the US system, which doubles letters instead (DD, DDD, DDDD). A woman wearing an Australian E cup is wearing a US DDD cup — same volume, different label.
- AU band sizes (8, 10, 12, 14) are based on underbust in cm, not inches
- AU uses UK cup letters (DD, E, F, FF, G) not US letters (DD, DDD, DDDD)
- AU 10 = UK/US band 34, AU 12 = UK/US band 36, AU 14 = UK/US band 38
- Cup letters are ratios — a C cup on AU 10 is physically smaller than a C cup on AU 14
- Sister sizes share the same cup volume across different band sizes
How to Measure Your Australian Bra Size
You need only two measurements to find your Australian bra size: your underbust (rib cage below the breasts) and your overbust (fullest part of the bust). A standard soft measuring tape and three minutes of careful attention will get you within one sister size of your perfect fit.
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1
Prepare correctly
Wear a non-padded bra or no bra at all. Padded bras distort measurements by adding several centimetres to your overbust reading. Stand naturally in front of a mirror with your arms relaxed at your sides.
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2
Measure your underbust
Wrap the tape snugly around your ribcage directly beneath your bust. The tape should be parallel to the floor all the way around — not sloping down at the back. Exhale fully and record the measurement in centimetres. This is your band measurement.
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3
Measure your overbust
Measure around the fullest point of your bust. Keep the tape loose enough to slide one finger underneath — you want the natural shape, not compressed. Again, ensure the tape stays horizontal across your back.
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4
Calculate your AU band
Match your underbust cm to the Australian band size. Each AU band spans a 5 cm range: AU 8 = 63–67 cm, AU 10 = 68–72 cm, AU 12 = 73–77 cm, AU 14 = 78–82 cm, AU 16 = 83–87 cm. If you fall on a boundary, try both sizes.
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5
Calculate your cup letter
Subtract your underbust from your overbust. The difference determines your cup: 11–13 cm = A, 14–16 cm = B, 17–18 cm = C, 19–21 cm = D, 22–23 cm = DD, 24–26 cm = E, 27–28 cm = F. This uses the AU/UK cup grading of roughly 2.5 cm per letter.
Remeasure every six months, or after any weight change of 3+ kg. Your rib cage and breast tissue both shift with hormonal cycles, weight fluctuations, pregnancy, and aging. Most Australian women wear the wrong size because they haven’t measured in years — not because sizing is confusing.
Skip the calculation — use the calculator
Enter your measurements once and get your exact AU size plus conversions to US, UK, EU, FR, and IT instantly.
Open the AU Bra Size Calculator →Australian Bra Size Chart (Underbust cm Reference)
This chart is the standard Australian sizing reference used by Berlei, Bonds, Bras N Things, and licensed fitters nationwide. It’s also the chart used by the Breast Cancer Network Australia’s My Care Kit program, which partners with Berlei to provide post-surgery bras.
| AU Band | Underbust (cm) | Underbust (in) | UK/US Band | EU Band | FR Band |
|---|---|---|---|---|---|
| AU 6 | 58–62 | 23–24.5 | 30 | 65 | 80 |
| AU 8 | 63–67 | 25–26.5 | 32 | 70 | 85 |
| AU 10 | 68–72 | 26.5–28.5 | 34 | 75 | 90 |
| AU 12 | 73–77 | 28.5–30.5 | 36 | 80 | 95 |
| AU 14 | 78–82 | 30.5–32.5 | 38 | 85 | 100 |
| AU 16 | 83–87 | 32.5–34.5 | 40 | 90 | 105 |
| AU 18 | 88–92 | 34.5–36 | 42 | 95 | 110 |
| AU 20 | 93–97 | 36.5–38 | 44 | 100 | 115 |
| AU 22 | 98–102 | 38.5–40 | 46 | 105 | 120 |
| AU 24 | 103–107 | 40.5–42 | 48 | 110 | 125 |
Australian sizes compared with US, UK, and EU systems
AU Cup to US, UK, EU Cup Conversion
This is the single most confusing part of Australian bra sizing. Australia uses UK cup letters, but many imported brands — especially American labels like Victoria’s Secret and ThirdLove — use the US doubled-letter system. The physical cup volume is the same; only the label differs.
| AU Cup | UK Cup | US Cup | EU Cup | Overbust − Underbust Difference |
|---|---|---|---|---|
| AA | AA | AA | AA | 8–11 cm (3.25–4.25 in) |
| A | A | A | A | 11–13 cm (4.25–5.25 in) |
| B | B | B | B | 14–16 cm (5.25–6.25 in) |
| C | C | C | C | 16–19 cm (6.25–7.25 in) |
| D | D | D | D | 19–21 cm (7.25–8.25 in) |
| DD | DD | DD | E | 21–24 cm (8.25–9.25 in) |
| E | E | DDD | F | 24–26 cm (9.25–10.25 in) |
| F | F | DDDD / G | G | 26–29 cm (10.25–11.25 in) |
| FF | FF | G / H | H | 29–31 cm (11.25–12.25 in) |
| G | G | H / I | I | 31–34 cm (12.25–13.25 in) |
| GG | GG | I / J | J | 34–36 cm (13.25–14.25 in) |
| H | H | J / K | K | 36–39 cm (14.25–15.25 in) |
Many online converters claim AU 10 equals US 32. This is wrong. AU 10 corresponds to an underbust measurement of 68–72 cm, which converts to a US/UK band size of 34, not 32. The myth persists because people assume AU sizing simply starts two numbers lower than US — but the relationship is cm-based, not a fixed offset.
What Are Sister Sizes in Australian Bras?
Sister sizes are bra sizes with the same cup volume but different band widths. They’re your safety net when your primary size isn’t stocked, when a bra runs slightly tight or loose, or when you’re buying across brands that run differently.
The sister size rule
To find your sister size, apply this principle: when you change the band by one size, you must change the cup letter by one step in the opposite direction to maintain the same cup volume.
- Smaller band, bigger cup letter: If your 12C feels too loose in the band, try 10D. Same volume, tighter fit.
- Bigger band, smaller cup letter: If your 12C feels too tight in the band, try 14B. Same volume, looser fit.
AU 12C sister size example
| Size | Band Feel | Cup Volume | When to Try It |
|---|---|---|---|
| AU 10D | Tighter | Same | Your 12C band rides up or feels loose |
| AU 12C | Standard | Same | Your primary size |
| AU 14B | Looser | Same | Your 12C band digs in or feels tight |
When shopping across brands, sister sizes become essential. A Berlei AU 12C may fit slightly differently from a Bras N Things AU 12C, even though the label is identical. Knowing your sister sizes means you always have a fallback that still fits the same cup volume.
Different breast shapes require different bra fits and styles
Australian Bra Brand Sizing Differences
Even within Australia, not all brands fit identically. Here’s how the major Australian and internationally-stocked brands run compared to the standard AU sizing chart.
The reference standard. Berlei’s sizing aligns exactly with the AU charts used by Breast Cancer Network Australia.
Fit: True to AU size. No adjustment needed.
Popular for wirefree and everyday comfort bras. Uses a slightly wider cup grading (2 cm per cup) than Berlei’s 2.5 cm standard.
Fit: Bonds cups run slightly smaller. If you’re a borderline cup, size up one letter.
Extensive range including their own label and international brands. In-house sizing follows AU standard closely.
Fit: True to AU in BNT’s own label; imported lines vary — check brand chart.
Stocks sizes AU 8–26. Their own label sizing sticks to standard AU charts; Target also carries international brands with their own quirks.
Fit: True to AU size. Cups may run slightly shallow in wire-free styles.
Uses US sizing on labels — 32, 34, 36 band and A, B, C, D, DD, DDD, DDDD cups. Tends to run small in the band and generous in the cup.
Fit tip: If you’re AU 12C, try 36C or sister-size up to 38B.
US-labelled sizes. Known for firm bands and shallow cups. Stocks limited range above DDD cup.
Fit tip: Runs tight in the band — size up one band (AU 12 → 36 US).
Offers half-cup sizing (e.g., 34B½). Ships to Australia but uses US labels.
Fit tip: True to US size. Convert your AU size, then pick half-cup up if your current bra feels slightly snug.
UK specialist for D+ cups. Uses UK sizing, which matches AU cup letters exactly. Band numbers are UK (so 34, 36, 38).
Fit tip: Convert your AU band (12 → 36 UK) and keep the same cup letter.
Signs Your Australian Bra Size Is Wrong
Even with correct measurements, your size can drift over time or differ between brands. Here’s how to diagnose a poor fit and which sister size to try.
Band size problems
- Band rides up at the back: band is too big. Try one size down in band, one cup up (e.g., AU 12C → 10D).
- Band digs into your ribs or leaves deep marks: band is too small. Try one size up in band, one cup down (e.g., AU 12C → 14B).
- Band pulls forward when you raise arms: band is too loose. Tighten hooks or size down.
Cup size problems
- Spillover at top or sides: cup is too small. Size up one cup letter (AU 12C → 12D).
- Gapping or wrinkling in the cup: cup is too big. Size down one cup letter (AU 12C → 12B).
- Underwire sits on breast tissue, not flat against ribs: cup is too small. Size up one cup letter.
- Straps digging in: usually a band problem. A well-fitting band carries 80% of bra support; tighten the band or size down.
If you’ve been wearing the same size for over two years without checking, you’re almost certainly in the wrong size. Australian fit specialists estimate 80% of women wear incorrectly sized bras. Rib cage volume changes with weight, hormones, pregnancy, and age — your bra needs to change with you.
Why Australian Bra Sizing Confuses Everyone
Australian bra sizing draws criticism for being overcomplicated — but once you understand its origin, the system actually makes more anatomical sense than the US alternative.
The dress-size inheritance
Australian band numbering (8, 10, 12, 14) evolved alongside the women’s dress sizing system. Early bra manufacturers, who often also made foundation garments, adopted the same numbering for continuity. A woman buying a size 12 dress naturally expected a size 12 bra to align — and it did, because both were built on the same rib-cage measurement.
The cm base (not inches)
Unlike the US system — which builds band size from inches plus an arbitrary offset (add 4 or 5 inches to underbust) — Australian bands sit directly on the centimetre measurement of your underbust. Your underbust cm is almost literally your band size, just divided by a factor and labelled with dress numbers. This is simpler and more accurate than the legacy US formula.
UK cup letters vs US doubled letters
The extended UK alphabet (A, B, C, D, DD, E, F, FF, G, GG, H…) handles large cup sizes with a unique letter for each 2.5 cm increment. The US doubled-letter system (DD, DDD, DDDD) becomes ambiguous and visually confusing past DD. Australia wisely adopted the UK convention — which is why any bra over D cup purchased from the US will have a label that looks wildly different from what you’re used to.
The three-label problem
Because Australia sits geographically closer to Asia, culturally closer to the UK, and shops heavily from the US, the average Australian shopper encounters three different labelling systems regularly. A single body size might be labelled:
- AU 12E (Australian retailers)
- 36E (UK brands like Bravissimo, Marks & Spencer)
- 36DDD (American brands like Victoria’s Secret)
All three describe the exact same bra. The calculator handles this translation automatically.
Stop guessing — get your exact size in 30 seconds
Our Australian Bra Size Calculator converts your cm measurements into AU, US, UK, EU, FR and IT sizes instantly. Includes sister sizes and fit diagnosis.
Use the Calculator →Shopping International Brands as an Australian
Buying imported bras online is the single most common way Australians end up with the wrong size. Each international labelling system has its own quirks. Here’s how to translate your AU size confidently.
Buying from US retailers
Convert your AU band to US by using the chart above: AU 10 = 34, AU 12 = 36, AU 14 = 38. For cup, translate UK/AU letters to US doubled letters only above D cup. A US 34B equals an AU 10B exactly. A US 36DDD equals an AU 12E.
Buying from UK retailers
This is the easiest conversion. AU and UK use identical cup letters. The only change is the band number: AU 10 = UK 34, AU 12 = UK 36. Your cup letter stays the same. An AU 12F is a UK 36F with no other adjustment needed.
Buying from European retailers
EU band numbers are based on underbust cm: AU 10 (68–72 cm) = EU 75; AU 12 (73–77 cm) = EU 80. EU cup letters run one letter higher than AU/UK for D+ sizes: AU DD = EU E, AU E = EU F, AU F = EU G. French and Spanish brands add 15 to the EU number — AU 12 is EU 80 but FR/ES 95.
Always check the brand’s specific size chart before purchasing. Even within the same country, individual brands have sizing quirks. Look for reviews that mention the reviewer’s usual size — if someone says “I’m normally a 12C and took my usual size,” that’s valuable fit data specific to that brand and style.
Frequently Asked Questions
Is AU 10 the same as US 32?
No. AU 10 corresponds to an underbust of 68–72 cm, which converts to a US/UK band size of 34, not 32. The myth that AU sizes are simply two numbers lower than US sizes is incorrect — the relationship is based on centimetre measurements, not a fixed number offset. AU 8 equals US/UK 32.
What is AU cup E in US sizes?
AU cup E equals US cup DDD. Australia uses the extended UK cup alphabet (A, B, C, D, DD, E, F, FF, G), while the US doubles letters instead (DD, DDD, DDDD). The physical cup volume is identical — a 26 cm difference between overbust and underbust corresponds to an AU/UK E or a US DDD.
Why does my AU size feel different in an imported US bra?
Two main reasons. First, US cup lettering differs beyond D cup (what Australia labels E is US DDD). Second, many US brands run small in the band and generous in the cup compared to Australian brands. If an imported US bra feels tight in the band but loose in the cup, try your sister size: go up one band and down one cup letter.
Do Bonds and Berlei use the same Australian sizing?
Mostly yes, with one difference. Both brands use AU dress-size bands (8, 10, 12, 14) and UK cup letters. However, Bonds uses a slightly wider cup grading — roughly 2 cm per cup letter — while Berlei follows the stricter 2.5 cm standard. Bonds cups therefore run slightly smaller than Berlei. If you’re borderline between cup sizes, size up in Bonds.
How often should I remeasure my bra size?
Every six months at minimum, or any time you experience weight change of 3 kg or more, pregnancy, breastfeeding, hormonal shifts, or noticeable fit changes. Your rib cage, breast tissue density, and muscle tone all change over time — a bra that fit perfectly a year ago may no longer fit correctly today.
What if I measure between two Australian sizes?
If your underbust falls on a boundary between AU bands (for example, exactly 73 cm could be the top of AU 10 or start of AU 12), try the smaller band first. Bra bands stretch with wear, so a band that feels slightly firm new will relax into the perfect fit within a few weeks. If the smaller band feels restrictive when you breathe deeply, size up.
Why are there so many cup letters in Australian sizing?
Australia uses the UK extended cup alphabet which provides a unique letter for each 2.5 cm of cup volume. The sequence runs A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K. This gives a precise label for each size, rather than the ambiguous US doubled-letter system (DD, DDD, DDDD) which becomes difficult to read and interpret above D cup.
Can I wear a sister size instead of my exact size?
Yes, and many women do without realising. Sister sizes share the same cup volume but have different band widths. If your AU 12C isn’t available in a style you love, AU 10D and AU 14B will fit your cup identically — you’ll just need to adjust the hooks or band expectations. This triples your shopping options across any brand.
What does AU 12DD mean?
AU 12DD is an Australian bra size with a band fitting 73–77 cm underbust and a cup volume representing a 21–24 cm difference between overbust and underbust. It’s the cup size between D and E in the UK/AU system. The US equivalent is 36DD; the UK equivalent is 36DD; the EU equivalent is 80E.
How accurate is measuring at home?
Home measuring is reliable within one sister size for about 85% of women. For the most accurate fit, measure with the help of a second person, wear a non-padded bra or no bra, and round to the nearest 0.5 cm. Professional fittings at Bras N Things, David Jones, or Myer can refine beyond this, but calculated sizes are an excellent starting point for online shopping.
What’s the largest Australian bra size available?
Major Australian retailers typically stock bands AU 8 to AU 24 and cups up to G or GG. Specialty stores like Bras N Things and online retailers like Brava stock extended ranges up to AU 26 and cups through K or beyond. Berlei’s professional range covers AU 10 to AU 24 in most standard cup sizes, making it one of the most size-inclusive Australian brands.
Does Australian bra sizing include inches?
Occasionally, but not as the primary system. Australian sizing is cm-based by default. Some brands list inch equivalents in their size charts for customers familiar with US or UK systems. An AU 12 corresponds to approximately 28–30 inch underbust. Converting cm to inches is straightforward: divide cm by 2.54.
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