Bra Size Calculator

Two quick measurements. Get your exact band and cup size in under 10 seconds.

cm
cm

Not sure how to measure? See the 3-step guide below.

How to measure

  1. Step 01

    Wrap the tape directly under your bust, level all the way round.

  2. Step 02

    Measure across the fullest part of your bust, tape snug not tight.

  3. Step 03

    Enter both numbers above. Your underbust sets the band, your bust sets the cup.

Bra size chart (AU)

Find your underbust row, then the bust range in that row — the column is your cup.

BAND SIZE (CM)ALPHA / NUMERICA CUPB CUPC CUPD CUPDD CUPE CUPF CUPG CUPH CUPJ CUPK CUP
57-62XXS / 670-7272-7575-7777-8080-8282-8585-8787-9090-9292-9595-97
62-67XS / 875-7777-8080-8282-8585-8787-9090-9292-9595-9797-100100-102
67-72S / 1080-8282-8585-8787-9090-9292-9595-9797-100100-102102-105105-107
72-77M / 1285-8787-9090-9292-9595-9797-100100-102102-105105-107107-110110-112
77-82L / 1490-9292-9595-9797-100100-102102-105105-107107-110110-112112-115115-117
82-87XL / 1695-9797-100100-102102-105105-107107-110110-112112-115115-117117-120120-122
87-922XL / 18100-102102-105105-107107-110110-112112-115115-117117-120120-122122-125125-127
92-973XL / 20105-107107-110110-112112-115115-117117-120120-122120-122125-127127-130130-132
97-1024XL / 22110-112112-115115-117117-120120-122122-125125-127125-127130-132132-135135-137
102-1075XL / 24112-117117-120120-122122-125125-127127-130130-132130-132135-137137-140140-142
107-1126XL / 26117-122120-125122-127125-130127-132130-135132-137132-137137-143143-146146-148

Your result

Sister sizes — same cup volume, different fit

Bra Size Calculator and AU, UK, US, EU Size Converter

Bra sizing is confusing enough before different countries start changing the numbers and letters. Enter your underbust and overbust measurements to estimate your AU bra size with this bra size calculator, find its closest UK, US, EU and French equivalents, and see two sister sizes you could try. This Australian bra size calculator is designed with fuller busts in mind, including C to H cups.

International Bra Band Size Chart (AU, UK, US, EU, FR)

AU/UK BandUS BandEU BandFR BandUnderbust (cm)
830658063-67
1032708568-72
1234759073-77
1436809578-82
16388510083-87
18409010588-92
20429511093-97
224410011598-102

Cups line up as A, B, C, D for the first few sizes across AU, UK and US. From DD upwards they diverge. The systems begin to differ above a D cup, and the same letter does not always represent the same cup volume in every country. Use this bra size chart calculator for a starting conversion, then check the individual brand’s chart before ordering. For the finer detail, here's a deeper international sizing breakdown. The bra cup size chart is only a starting point because cup progressions differ between Australian, UK, US and European brands.

One honest note. This chart converts the label, not the body. A UK 34F and a US 34G share a nominal size but can fit completely differently depending on how a brand grades its patterns.

Sister sizes: a quick fix, not a forever fit

A sister size has the same cup volume but a different band. Go one band up and one cup down (12D becomes 14C), or one band down and one cup up (12D becomes 10DD). This bra sizing guide can help you understand when to try a sister size.

Your sizeSister upSister down
10D12C8DD
12DD14D10E
14F16E12FF

Use this bra size chart calculator for a starting conversion, then check the individual brand’s chart before ordering. Skip it if the gore won't tack to your sternum, or the wires sit on breast tissue instead of ribcage. Sister sizing is a band-aid, not a solution. For the long game, go to our sister sizing deep dive.

5 signs your bra actually fits

  • Band: level front to back, snug enough for two fingers underneath. Band's doing the heavy lifting.
  • Cups: contain the lot. No spillage, no gaping, no quad-boob.
  • Straps: support, don't dig. Along for the ride, not holding you up.
  • Centre front (gore): tacks flat to your sternum between the breasts.
  • Wires: sit on your ribcage, not on breast tissue.

Curious about what each part of a bra size means? We've broken it down.

Why your bra size keeps letting you down (and how to fix it)

1. Measuring in a padded bra.

Padding can alter your overbust measurement. Measure in an unpadded bra, or braless if that feels comfortable.

2. Using the +4 inches method.

It's dead. It was built for stiff fabrics with no stretch. Nala’s sizing method does not add four inches. Instead, it uses your snug underbust measurement to find the corresponding Australian band size in the chart above. This bra measurement guide provides a simple starting point for finding your size. For example, an underbust of 78–82 cm maps to an AU 14.

3. Trusting a converter label across brands.

A 34F in one brand fits nothing like a 34F in another. Always cross-check with the brand's own chart in cm.

4. Relying on one uncertain reading.

Measure twice and average the results if they differ.

5. Expecting your size to stay still.

Pregnancy, cycle, weight and even stress change it. Remeasure every six months, or whenever a bra stops feeling right. If you're in C+ territory, our fuller-bust bras for C to H cups are a great place to land.

From our Fit Whisperer

The number one thing I see? People measuring in a padded bra and ending up two cup sizes too big and a band too small. Ditch the bra, measure three times mid-morning, and trust the cm reading over any formula. Your underbust in centimetres is almost always your AU band. Everything gets easier from there.

Nala Lead Fit Specialist

Got your number? Go find your fit.

Now you've got your size, shop bras in your size or browse wirefree bras in your size. Still unsure? Try the Nala Fit Guide or contact the Nala team for sizing help.

Note: This bra and cup size chart provides an estimate and a starting point. Fit varies by brand, style, fabric and breast shape.

More on fit

Take the Fit Guide Read the blog Sizing FAQ

Bra size calculator FAQs

Is my size the same in every brand?

Short answer: no. A bra size chart is a starting point, not gospel. Brands grade patterns differently, so a 12D at one label can fit like a 10DD at another. Always measure in cm and compare to the brand's own cup size chart before you commit.

What if I'm between sizes?

Try your sister size first. If your band feels loose but the cup fits, go down a band and up a cup. If the cup is tight but the band is spot-on, stay in the band and go up a cup. Our bra sizing guide and the bra size calculator above both suggest sisters automatically.

How often should I measure?

Every six months, or anytime a bra stops feeling right. Weight shifts, hormones, and even which bras you've been wearing all nudge your size. A quick bra measurement check using a bra size calculator beats putting up with a bra that digs.

Does my bra size change in pregnancy?

Yes, often significantly. Band and cup can both grow, usually from the first trimester onward and again around milk coming in. Measure every few weeks and lean on soft, wire-free styles. Rigid wires on changing tissue is a hard no.

What's a sister size and when should I use it?

A sister size shares the cup volume but swaps the band (e.g. 12D and 14C). Use it when you're between sizes or testing a new brand. Don't rely on it long term, especially with a fuller bust. The right band and cup combo is what gives you real support. For style guidance, see which bra style suits your shape.

Should I measure with or without a bra?

Braless gives the most accurate result. If you'd rather measure in a bra, wear a non-padded one so it doesn't add to your bust measurement.