Although many women express their desire for breast surgery in terms of bra size, bra sizing is rarely discussed by plastic surgeons. I decided to learn bra measurement to better meet the needs of my patients, but I soon discovered that the traditional method of bra sizing was confusing and inaccurate, with most lingerie department personnel unable to explain to me how they determined bra size other than by trial and error. I began to see why so many women are said to wear the wrong size bra.

Consider band size, which is the simpler of the two measurements that make up a bra size—the other measurement is cup size. For example, in a 36C bra, 36 is the band size and “C” is the cup size. Band size is determined by measuring the circumference of the chest under the breasts (this is called the rib cage or underbust measurement) and adding “5” to that number. For example, if the rib-cage measurement is 31 inches, then the band size is 36.

However, 36 is a size and not a measurement. A size 36 bra measures around 27 inches in length, or circumference. A bra’s elastic can stretch to the 31 inches necessary to fit around a woman’s chest, and would be as tight as a drawn bow if stretched to 36 inches.

Cup size measurement is even more confusing. All traditional methods of bra measurement are variations of a scheme that determines cup size by the relationship of the chest circumference near the breasts to the circumference above or below the breasts.

This method is so inaccurate as to be useless. I found that bra sizes were off by two or more cup sizes.1

This 24-year-old woman requested augmentation from an “A” cup to a “C” cup in a size 34 bra. She is shown before and 6 months after submuscular breast augmentation with 350-cc silicone gel-filled implants. Preoperative measurements showed a breast width of 6.5 inches with an underbust circumference of 29 inches, corresponding to a 34A bra size. Postoperative measurements are 8.5 and 29 inches, corresponding to the 34C bra that she now wears.

In the mid-1990s, I began taking careful measurements of my augmentation patients before and after surgery and correlating the numbers to the size bra they reported as fitting best and to different bras they tried on in my office. Imagine my joy when I realized that cup size should be determined by direct measurement of the breast.

Eventually, I came up with a measuring system wherein, say, a breast with a 7-inch width (measured across the fullest part of the breast, from its origin on the lateral chest wall to the point where it ends near the sternum) was an “A” cup, 8 inches a “B” cup, 9 inches a “C” cup, and so forth.1

This system works best for women wearing a size 36 band but was less accurate with much smaller or larger band sizes.

Next, allow for the fact that cup size varies with band size. That is, the “C” cup of a size 36 bra is larger than the “C” cup of a size 34 bra, yet it is not as large as the “C” cup of a size 38 bra.

Further investigation revealed that, for example, if a breast width of 9 inches was a “C” cup in a size 36 bra, a width of 8.5 inches was a “C” cup in a size 34 bra, whereas 9.5 inches was necessary to fill a “C” cup in a size 38 bra.2

This sliding-scale relationship of breast width to underbust circumference is incorporated into the bra- sizing slide chart available at

I now use this measuring system on all breast surgery patients. If a woman who wears a 34A bra preoperatively wants to become a “C” cup size, I augment her breast width intraoperatively from 6.5 inches to 8.5 inches. Conversely, if a woman who wears a 36E cup preoperatively wants to become a “C” cup, I reduce her breast width from 12 inches to 9 inches.

See also “The Second Time Around” by Lori L. Cherup, MD, FACS, and Tiffany A. Gleason, PA-C, in the October 2006 issue of PSP.

Although some women choose to wear a bra that doesn’t fit properly by the usual criteria, and many women fit well into more than one size bra, this system gives an accurate bra measurement at least 90% of the time.

I ask all of my postoperative patients, “How is the size of your breasts in relation to what you had asked for?” It is rare when they do not answer, “Perfect.”

Edward A. Pechter, MD, FACS, is certified by the American Board of Plastic Surgery and has practiced in the Santa Clarita Valley in California for 25 years. He can be reached at


  1. Pechter E. A new method for determining bra size and predicting postaugmentation breast size. Plast Reconstr Surg. 1998;102: 1259-1265.
  2. Pechter E. An improved technique for determining bra size with applicability to breast surgery. Plast Reconstr Surg. In press.