Australian bra sizes use a number (band size for ribcage circumference) and a letter (cup size for bust fullness), measured in centimeters, where the cup size is the difference between your underbust and overbust (fullest part of bust) measurements, increasing by 2cm per cup letter (A, B, C, D, DD, E) with each band size progression (8, 10, 12). A crucial concept is sister sizing, meaning a 10DD has the same cup volume as a 12D, as you go up a band size and down a cup size to maintain volume.
To measure your Australian bra size, find your underbust band size by measuring snugly around your ribcage (in cm) and your bust cup size by measuring loosely around the fullest part of your breasts (also in cm); then, subtract the band from the bust measurement, where a 12-13 cm difference is an A, 14-15 cm a B, 16-17 cm a C, 18-19 cm a D, and so on, using standard AU band sizes (like 10, 12, 14) and converting the difference to a letter cup size.
No, 12B and 10C are not the same size but are considered sister sizes, meaning they have roughly the same cup volume but different band lengths, making them good alternatives when your usual bra doesn't fit perfectly. A 12B has a larger band (12) and a smaller cup (B) than a 10C, so going from 12B to 10C gives you a smaller band (firmer fit) and a larger cup (C) to maintain similar fullness.
A means a 1-inch difference, B is 2 inches, C is 3, and D is 4. Cup size increases with both letter and band size. Understanding ABCD in bra sizing helps you choose the right fit. Understanding bra sizes can feel like decoding a secret language, especially when letters like A, B, C, and D come into play.
A 36C bra size in the US/UK is equivalent to a 14C in Australian (AU) sizing, using the band size 14 with the same C cup. This means you'll look for a size 14C when shopping in Australian stores, with the band size corresponding to the UK/US 36.
36C is a bra size that represents a moderately sized band with a C cup. In terms of breast size, it is considered to be in the average range. The number 36 refers to the band size, which is the measurement around the torso just below the breasts.
The two-finger rule for bras is a quick test to check your band's fit: you should be able to comfortably slide two fingers (stacked or side-by-side, depending on the source) under the band at the back or front. If you can fit more, the band is too loose; if you can't fit two, it's too tight, meaning the band is either not providing enough support or is causing discomfort. A properly fitted band carries most of the breast weight, keeping the bra level and straps from digging in.
The "3 bra rule" is a guideline recommending you own at least three bras for a simple rotation: one to wear, one to wash, and one to rest (in the drawer), allowing elastic to recover between wears to extend the bra's lifespan and maintain fit. This system prevents wearing the same bra daily, which stretches out the elastic and reduces support, helping bras last longer.
You'll remember that this measurement is the distance between your bust point and the base of the breast where it meets the rib cage. A measurement of 2 1/2" (6.5 cm) indicates an A Cup, 3" (7.5 cm) is a B cup, 3 1/2" (9 cm) indicates a C cup and so on with each cup size increasing by an average of 1.25 cm or ½".
For example, if you measure at a size 34D, your sister sizes are 32DD and 36C. They are the sizes directly left and right of 34D size in the chart. These bras hold the same volume, but at a different band size. At 32DD you'd have a much firmer band, whereas 36C would be a more relaxed feel without the loss of support.
Asian and African nations have the smallest, with predominantly B and A cup sizes being most common. Australia is way down the list: in 2020, the most common Australian bra sizes are reported to be 14C and 12D, and while this is the average across all ages, there really is no such thing as the “average” woman.
It's not unusual to go up or down a whole cup size during normal breast development. Then, as you get older, you may notice that there is a wider space between your breasts and that the breast themselves have shrunk in size.
Padded bras usually have wide straps and an underwire, so all of these can give large breasts optimum support. Non-padded bras do not offer as much support, primarily because of no foam lining.
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A: D cup is bigger than a C cup. The difference between a C cup and a D cup is one inch. If a C cup represents a 3-inch difference between the bust and band size, a D cup represents a 4-inch difference.
To calculate your cup size, minus your band size from your overbust measurement - this difference will indicate your cup. These are the current bra sizes in Australia: 0 = AA, 1 = A, 2 = B, 3 = C, 4 = D, 5 = DD, 6 = F, 7 = FF, 8 = G, 9 = GG, 10 = H, 11 = HH, 12 = J, 13 = JJ, 14 = K and so on.
Yes, a D cup is generally considered a full or larger bust size, but its actual size varies greatly depending on the band size, and it's often not as large as cultural perceptions suggest, with many people who think they have smaller busts actually needing a D cup or larger for a proper fit. The cup size reflects the difference between your bust and band measurement (4 inches for a D cup), so a 34D is much smaller in volume than a 40D, though both are "D cups".
Cup size is always relative to the band size. That means a 36C has more cup volume than a 34C, even though they share the same cup letter. ...and so on.
Just as your size can fluctuate monthly, it can also change with other shifts in your body. Significant weight changes are a common reason for a new bra size. In fact, it often takes a weight loss or gain of 15 to 20 pounds for most women to see a noticeable change in their cup size.
The two-finger rule for bras is a quick test to check your band's fit: you should be able to comfortably slide two fingers (stacked or side-by-side, depending on the source) under the band at the back or front. If you can fit more, the band is too loose; if you can't fit two, it's too tight, meaning the band is either not providing enough support or is causing discomfort. A properly fitted band carries most of the breast weight, keeping the bra level and straps from digging in.
Because bras need time to rest and recover between wears to maintain their shape and support. Wearing the same bra two days in a row can cause the elastic to stretch out faster, reducing its lifespan. The rule of thumb? Wear it, rest it, wear it, wash it.
No matter the type of bra, the band should fit comfortably around your body, snug but not tight. Remember to always start a new bra on the loosest hook and hook tighter as the band stretches over time.
Sister sizes
For an example, a 32C and a 34B are the same cup size. The only difference is the band size. The 34 is a bigger band size than a 32.
The adhesive used in sticky bras can cause skin rashes and irritation, especially if the silicone cups are made using low-quality materials. Additionally, the sticky bra may become less effective after being worn for longer than the recommended eight hour maximum.