One of the most common questions asked by patients who are interested in breast augmentation or reduction surgery, is what bra size they will be after the procedure. It is a very interesting question but despite having years of experience in the field of Plastic Surgery, it is impossible to provide an exact answer. This is because the issue of bra fitting is far from being an exact science and there are too many variables.

It has been suggested around 70-100% of women wear the wrong sized bra. In one study (1), 80% of women wore incorrectly sized bras: 70% wore bras that were too small, 10% too large and in particular, large breasted women were more likely to do so. In order to understand this further, it is interesting to look into the variables that make it so difficult to choose and wear the right bra.

Bra sizing techniques

In 1935, an American company (Warner®) incorporated breast volume into the bra size specification and the alphabet bra was launched with cup sizes ranging from A to D (2). This method of alphabetical labelling allowed for communication between customers, retailers, manufacturers and designers. The calculation was based on the difference between the under bust chest circumference (UBCC) and the circumference of the chest around the fullest projection in a bra (over bust chest circumference/OBCC). This is also known as the Traditional method and now is the most common technique employed by retailers such as Marks & Spencer.

The second technique is the Hemi-circumference measurement, where the cup measurement is based on the distance between the lateral inflexion point and the medial inflexion point

The third technique, known as Professional bra measurement, takes into account the way the strap lies, the filling of the bra (over/underfill), band and underwire. The fitting is carried out by professionals who are trained by manufacturers and they assess the fit of the component part of a bra against set criteria. One study demonstrated that there was a difference on average of one cup size between the professional and traditional bra fitting method (2).

There are issues when it comes to the traditional method which is supposed to standardize cup sizing. This method measures the Band size by measuring the UBCC plus an arbitrary number. However, this measurement can be variable during inspiration and expiration. OBCC can also vary with the degree of ptosis and in particular, bra sizes bigger than the original A-D, there is even more variability between the different manufacturers. With the hemi-circumference technique, this is also the case. In addition, the issue of cross fitting between different bra sizes with the same hemi-circumference value, that is a C cup in a 32-inch band size or a B cup in a 34-inch band size. It may not seem significant but Smith et al showed that there was a wide range of breast volumes for just one reported cup size, 34D, which ranged from 594cm3 to 962cm3. To add to the variability of measurement technique, different manufacturers are inconsistent in their sizing, (4), each having their own individual size and grading system (5). To complicate matters further, anecdotal evidence suggest that many women simply select their own bra size based on their personal preferences.


There are hundreds of different manufacturers and they are all using different materials. In general, it’s a combination of cotton, nylon, polyester, silk, Spandex and microfibers. Without even going into the biomechanical details, all these materials have different elasticity, support and durability, in addition, bras will vary as to how good the material feels and look after a few washes. Changes in material support and under wiring also alter the measurements in many cases contributing to the overall comfort.

Breast Augmentation

For those patients who have had a breast augmentation, the hemi-circumference technique developed a system that uses the circumference of the breast as a predictor of bra cup size (6). Bengston & Glickmans study (7) identified variability between different manufacturers and the changes in cup size also varied between shaped and round implants and different projections. (kings)

Breast Reduction

With a variable baseline, it is particularly important to evaluate patients seeking reduction mammoplasty, many of whom are often incorrectly sized because of large breast volume and increased body mass index. As mentioned, the original alphabet sizing only goes up to D and the bra sizing becomes more diverse in the larger sizes between manufacturers. The volume of surgical reduction is affected by many factors including chest width, breast density and degree of ptosis.

Whether it be augmentation or reduction, evidence shows that that baseline bra measurement is likely to be wrong in many cases and it may still be wrong with the new fitting after surgery (8,9).The true value in surgical intervention is to improve the overall proportion and to identify a size that patient is happy with rather than be fixated on the exact cup size.

Your surgeon can guide and give you suggestions and options but ultimately, it is impossible to guarantee size as this is highly variable depending on the fitting, the brand and shape of the breasts. Implant size trial is helpful for augmentation, and in the end, the most important factor is your own perception of what your preference is and your surgeon can guide you as to what is suitable for your frame. Similarly, with breast reduction, the aim should be a breast that is in proportion with a good shape and projection.

With all this said, it is very important to wear a well-fitting bra. Ill –fitting bras and those providing insufficient breast support can lead to the development of musculoskeletal pain and inhibit women participating in physical activity.

Breast size, bra fit and thoracic pain in young women: a correlational study. Wood K et al. Chiropractic & Osteopathy 2008

Evaluation of professional bra fitting criteria for bra selection and fitting in the UK. White J, Scurr J. Ergo 2012

What is the standard volume to increase a cup size for breast augmentation surgery? A novel three-dimensional computed tomographic approach. King NM et al. PRS 2017

How do respiratory state and measurement method affect bra size calculations? McGhee DE, Steel JR. J of Sports Med 2006

Communications: the bra design process- a study of professional practice. Int J of Clothing Science and Technology 1997.

A new method for determining bra size and predicting post-augmentation breast size. Pechter EA PRS 1998

The standardization of bra cup measurements. Redefining bra sizing language. Bengston BP, Glicksman CA.

What is the standard volume to increase a cup size for breast augmentation surgery? A novel three-dimensional computed tomographic approach. King N.P. et al. PRS 2017

Reduction Mammaplasty: what cup size will I be? Chan M et al. PRSGlobal Open 2019