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You have been buying bras your whole life and somewhere in the back of your mind there is a small, slightly embarrassing question you have never fully answered. What do these letters actually mean? You know you are a 34B or a 32C, but why B? Why not just a number? What is the difference between a B cup and a C cup — is it really that significant? And what even happens after D?
If you have been guessing, sizing by feel, or just buying whatever felt closest to right in the trial room, you are genuinely not alone. Studies consistently show that the majority of women are wearing the wrong bra size, and a huge part of that problem is not the measuring — it is the understanding. Once you know what the letters actually represent, the whole system clicks into place. So let us break it down properly, once and for all.
Before we get into the letters, let us establish the full picture. Every bra size is made up of two parts: a number and a letter. When you see 34B written on a bra tag, the 34 is your band size and the B is your cup size. These two pieces of information together tell you everything about what your bra needs to do for your body.
The number is your band size, which is the measurement around your ribcage just under your bust. The band is responsible for about 80 percent of the support your bra provides. It is doing the heavy lifting — literally. The straps are really just there to hold the cups in position, not to carry weight.
The letter is your cup size, which tells you the volume of the cups. And this is where most women get confused, because the letter does not mean what most people assume it means.
Here is the part that genuinely surprises most women. The cup letter is not a fixed measurement. It is not like a shoe size where a size 6 means a specific foot length regardless of anything else. Your cup letter is a ratio — specifically, it is the difference in centimetres or inches between your bust measurement and your band measurement.
This is how it works:
So if your underbust measures 32 inches and your bust at the fullest point measures 35 inches, the difference is 3 inches, which makes you a C cup. Your full bra size would be 32C.
If your underbust measures 34 inches and your bust measures 37 inches, the difference is still 3 inches — but your bra size would be 34C, not 32C. Same letter, different number, different bra entirely. This distinction is important and we will come back to it.
This is one of the most persistent myths in lingerie and it genuinely causes women to buy the wrong bras for years. Because of the way D cup is talked about in popular culture, many women assume D means extremely large. It does not. A D cup simply means your bust measurement is 4 inches larger than your underbust measurement. That is it.
A 30D — a 30-inch band with a D cup — is actually a relatively petite bra on a small-framed woman. The cup volume in a 30D is quite modest in real-world terms. A 38D on the other hand, with a much larger band, contains significantly more breast volume even though both technically say D on the tag.
This is why women with smaller frames sometimes feel confused when they measure as a D cup and it seems wrong. It is not wrong. The letter is telling you about the difference between your measurements, not about a universal breast size category.
India follows the UK bra sizing system, which uses a specific sequence of cup sizes after D. Understanding where D sits in the full scale gives you proper context for where your size falls.
The scale runs like this:
| Cup Letter | Difference Between Bust and Underbust |
|---|---|
| AA | Less than 1 inch |
| A | 1 inch |
| B | 2 inches |
| C | 3 inches |
| D | 4 inches |
| DD | 5 inches |
| E | 6 inches |
| F | 7 inches |
| FF | 8 inches |
| G | 9 inches |
Most Indian lingerie brands — including Amour Secrt — primarily stock A through D cups, with some styles extending to DD. This is because the majority of Indian women fall within the B to D cup range. If you measure beyond D, you are looking for fuller-bust specialist sizing.
This is the concept that changes everything once it lands, and it is the reason why so many women feel confused when a bra that is technically their size just does not fit right in a different brand or style.
A 32C and a 36C are not the same cup. They share the same letter but they do not contain the same volume. The cup in a 36C is physically larger than the cup in a 32C, because the cup size is always calculated relative to the band it sits on. A 36-inch band with a 3-inch difference gets you a 36C. A 32-inch band with a 3-inch difference gets you a 32C. The difference is the same but the actual body it belongs to is different, and so is the cup.
This is why you cannot just hand someone a bra and say "it is a C cup, it should fit you." The number matters just as much as the letter, and you need both to find a bra that actually does its job.
If you have been measuring yourself but are not sure whether you have the calculation right, the Amour Secrt size guide walks you through the full process step by step, and the how to measure bra size at home guide gives you the practical tape-measure instructions with examples.
Once you understand that cup size is a ratio, a very useful concept opens up — sister sizing. Sister sizes are bra sizes that share the same cup volume but have different band sizes. Because the cup size is always measured relative to the band, when you go up one band size you need to go down one cup letter to maintain the same cup volume. When you go down one band size you need to go up one cup letter.
A practical example:
Why does this matter for Indian shoppers specifically? Because online shopping is now the default for most Indian women buying lingerie, and stock availability varies. If your usual 34B is sold out in the colour or style you want, knowing that 32C holds the same cup volume means you are not stuck. You might also find that one sister size fits your body better than your technically correct measurement, depending on your breast shape and torso.
Sister sizing also helps when you are between sizes. If a 34B feels slightly too loose in the band but a 32B feels too tight in the cups, 32C is worth trying — tighter band with slightly more cup volume than the 32B.
Knowing your cup size letter is not just about ordering the right size. It actually tells you something about which bra styles and constructions are going to work best for your body. This is the practical payoff of understanding the measurement system.
A cup — Softer, lighter construction works beautifully here. Bralettes, triangle bras, lightly padded everyday bras, and bandeau styles all suit A cups well because the cup does not need to manage significant volume. Padding adds shape definition without bulk.
B cup — The most versatile cup size in terms of available styles. B cup works across almost every bra construction — T-shirt bras, seamless bras, balconettes, padded and non-padded options. Both seamed and moulded cups work well.
C cup — A C cup benefits from a little more structure in the cup, particularly for everyday wear. Moulded T-shirt bras, lightly padded styles with full coverage, and bras with side support panels all work particularly well. A C cup typically does not need underwire to feel supported in a well-constructed wireless bra.
D cup — At D cup, the cup construction starts to matter more. Full coverage bras provide better containment than demi cups for most D cup bodies. If you are shopping for a sports bra, D cup needs a high-impact style with proper compression and either a racerback or reinforced strap design. For everyday wear, seamed cups or moulded full-coverage styles give the best lift and shape.
For women with a fuller bust in the D to DD range, the plus size bra guide for Indian women covers style recommendations in much more detail, including which cup constructions provide the best support for heavier busts specifically.
Most women have been wearing the same bra size since they first worked it out — possibly in their teens — without reassessing. Bodies change. Sizes change. And many women are not so much wearing the wrong size as they are wearing a size that was right once and is no longer quite right now. Here are the signs your cup size needs a second look:
If more than one of these describes your current bra situation, it is probably time to re-measure rather than just buying the same size again.
You do not need a professional fitting to find your correct cup size. All you need is a soft measuring tape and two minutes.
Step 1 — Measure your underbust (band size) Wrap the tape snugly around your ribcage, directly under your bust. Keep it level and breathe normally. Round to the nearest even number. If the measurement is 31 inches, your band size is 32. If it is 33, round to 34.
Step 2 — Measure your bust Wrap the tape around the fullest part of your bust. It should be level all the way around and not too tight — the tape should just skim the surface of the breast without pressing in.
Step 3 — Calculate the difference Subtract your band measurement from your bust measurement. Match the difference to the cup scale:
If your underbust is 34 and your bust is 37, the difference is 3 inches, which gives you a C cup. Your size is 34C.
For a full walkthrough with visual guidance on getting the tape in the right position, the how to measure bra size at home guide covers every step in detail. And once you have your measurements, the Amour Secrt size guide lets you cross-reference to confirm your size before you shop.
The letters A, B, C, D represent cup sizes, which indicate the difference between your bust measurement and your underbust measurement. A is a 1-inch difference, B is 2 inches, C is 3 inches, and D is 4 inches. The letters are not fixed measurements — they are always relative to the band size number they sit next to.
D cup is not inherently large. Because cup size is relative to band size, a 30D on a small-framed woman can be quite modest in real-world volume, while a 38D on a larger frame contains significantly more. D simply means the bust measurement is 4 inches larger than the underbust measurement. Whether that reads as large depends entirely on the band size it is paired with.
B and C cups are the most commonly worn sizes among Indian women. Most Indian lingerie brands, including Amour Secrt, stock the deepest range of styles in B and C cups for this reason, though A and D cups are also well-represented in the collection.
India follows the UK sizing system. After D comes DD, then E, F, FF, G and beyond. DD means a 5-inch difference between bust and underbust, E means 6 inches, and so on. Most mainstream Indian brands stock up to D or DD. For sizes beyond DD, specialist fuller-bust brands carry extended sizing.
No. Even though both are B cups, the cup in a 36B is physically larger than the cup in a 34B. Cup size is always calculated relative to the band, so the actual cup volume changes as the band size changes. Two bras with the same cup letter but different band numbers are not the same size.
Sister sizing is when bras with different band and cup letter combinations hold the same cup volume. For example, 32C, 34B, and 36A are sister sizes — they all contain the same cup volume, just with different band widths. Sister sizing is useful when your exact size is unavailable in a particular style, or when you want to adjust the band tightness without losing cup volume.
The most common signs of a too-small cup are: breast tissue spilling over the top or sides of the cup, the centre gore not lying flat against your sternum, and the underwire sitting on breast tissue rather than encircling it cleanly at the base. If any of these apply, try going up one cup size in your current band size.
Yes, cup size can change with weight fluctuation, hormonal changes, pregnancy, breastfeeding, menopause, and even different stages of the menstrual cycle. It is a good idea to re-measure every six to twelve months, or any time your current bras consistently feel different from how they used to fit.
Because bra sizing is not fully standardised across brands globally. A 34C from one brand may have slightly different cup depth, width, and shape than a 34C from another. The letter and number tell you approximately where to start, but factors like cup shape, underwire placement, and fabric stretch all affect the actual fit. This is why sister sizing and trying different styles within your size range is always a good idea.
Yes. In the cup size sequence, each letter represents approximately 1 additional inch of difference between the bust and underbust measurement. B cup (2-inch difference) holds more volume than A cup (1-inch difference). C holds more than B, D holds more than C, and so on up the scale.
For C cup, full-coverage moulded T-shirt bras, seamed cup everyday bras, and lightly padded styles with side support panels all work well. For D cup, full-coverage styles with structured cups give the best support and lift. High-impact sports bras are essential for D cup women during exercise. Both C and D cups benefit from a firm, well-fitted underband which does most of the support work.
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