What Is a 12B Bra? Understanding Size and Fit

A 12B bra, typically referred to as a 12B size, is a specific measurement and style of brassiere designed to provide proper support and comfort for individuals with a cup size of B and a band measurement of 12. This particular bra size is part of the standardized sizing system used in the fashion industry to cater to a wide range of body types.

Is a 10D Bra the Same as 12C?

When it comes to bra sizing, it’s common for people to assume that a 10D bra and a 12C bra are completely different. However, the concept of “sister sizes” or “cross over sizing” allows us to understand that the cup volume of these bras is actually the same. A 10D bra, a 12C bra, and even a 14B bra, all have cups that hold the same amount of breast volume.

You might be wondering how this is possible. Well, bra sizes are made up of two components: the band size and the cup size. The band size refers to the measurement around the ribcage, while the cup size represents the volume of the breast. In sister sizing, a larger band size with a smaller cup size can hold the same volume as a smaller band size with a larger cup size.

The Difference Between Band Sizes and Cup Sizes in Bra Sizing

Band sizes and cup sizes are distinct measurements used to determine the right fit for bras. Band size refers to the measurement around one’s ribcage, while cup size measures the difference between the band size and the fullest part of the bust. For example, a band size of 34 indicates a ribcage measurement of 34 inches, while a cup size of B suggests a difference of around 2 inches between the band size and bust measurement. The combination of band and cup sizes helps in finding the most comfortable and supportive fit for individuals.

When it comes to bra sizes, it’s important to have a reliable conversion table to ensure a proper fit. For those wondering about a size 12, let’s explore the corresponding sizes in Australia and New Zealand, the United Kingdom, and the United States.

What Bra Size Is 12?

Determining the equivalent bra size can be confusing, especially when dealing with different sizing systems across various countries. For those wondering what bra size is 12, we can refer to the common size conversion table. In Australia and New Zealand, a bra size of 12 is roughly equivalent to a 34 in the UK and USA sizing systems.

This indicates a smaller cup size with a band size of 34 inches. Similarly, a 12B in Australia is equivalent to a 34B in the UK and USA. This implies a slightly larger cup size than a 12A, but with the same band size of 34 inches.

Here, the cup size increases again, while the band size remains the same.

It’s worth noting that these bra size conversions may vary slightly depending on the brand and specific style of the bra. Therefore, it’s advisable to refer to a size chart provided by the manufacturer or retailer to ensure the best possible fit. Taking accurate measurements of your bust and underbust can also help in determining the appropriate bra size for your body.

How to Care for and Extend the Lifespan of Your Bras.

  • Hand wash bras with a gentle detergent
  • Avoid using machines or dryers
  • Don’t wring or twist bras
  • Let bras air dry flat
  • Store bras properly to maintain shape
  • Rotate bras to prevent wear and tear
  • Use bra extenders for a better fit
  • Wear bras on the loosest hook first
  • Avoid wearing bras for multiple days in a row
  • Avoid direct heat or sunlight exposure
  • Replace bras when they no longer provide support
  • Consult a professional for proper bra fittings

Source: Bra Size Conversion Table – She Science

If you’re looking for a different band size to achieve a better fit, the sister size of a 14D bra would be 12DD for a firmer fitting band. On the other hand, if the band feels too tight, you can go up a back size and down a cup size to find your sister size of 16C.

What Is the Sister Size of a 14D Bra?

When it comes to finding the perfect fit for your bra, understanding sister sizes can be incredibly helpful. So, if you’ve been wearing a 14D bra but desire a firmer fitting band, your sister size would be 12DD. This means that while the cup size remains the same, the band size decreases by two sizes. By opting for a smaller band size, you can ensure a more snug and supportive fit, ideal for those who prefer firmness.

Conversely, if you find that your band feels too tight, you’ve the option of going up a back size and down a cup size to achieve a more comfortable fit. This allows you to increase the band size by two sizes while decreasing the cup size by one size. Such adjustments enable you to find the balance between comfort and support, ensuring that your bra fits you just right.

It’s crucial to note that sister sizing isn’t a one-size-fits-all solution, as every individuals body shape and preferences vary. Additionally, brands may have slight variations in their sizing charts, so it’s essential to be aware of these differences and make adjustments accordingly.

Remember, finding the perfect bra is a journey, and it may take some trial and error to discover the right fit for you. Your comfort and confidence are paramount, and a well-fitting bra plays a significant role in enhancing both.

How to Measure Your Bra Size Accurately

  • Start by wearing a non-padded bra and stand in front of a mirror.
  • Use a soft measuring tape to measure your underbust. Ensure the tape is level and snug.
  • Round up the measurement to the nearest whole number for your underbust size.
  • Next, measure around the fullest part of your bust. Make sure the tape is parallel to the ground.
  • Subtract your underbust measurement from your bust measurement.
  • Refer to a bra size chart to find your cup size based on the difference obtained.
  • Combine your underbust and cup size to determine your accurate bra measurement.
  • It’s recommended to try on different bra styles and sizes to find the one that offers the best fit and comfort.
  • Remember that bra sizes may vary between brands, so it’s essential to try on different options.
  • Don’t hesitate to seek assistance from a professional bra fitter if needed.


It caters to those who require a slightly larger cup size, providing proper support and comfort for a fuller bust. By understanding the significance of this size, we acknowledge the diverse needs and body types of individuals, promoting inclusivity and body positivity in the fashion industry. It’s essential to appreciate the uniqueness of each individual and embrace a broad spectrum of sizes, ensuring that all women feel confident and empowered in their own skin.