Breast size is unique to each woman and is influenced by several factors, including genetics, nutrition and diet, weight and body mass index (BMI), fitness level, and age. A woman’s breast size is not constant and often varies depending on her menstrual cycle and whether she is pregnant or nursing. It also has no relation to the number of births per day, nor to breastfeding rates or even the notably unscientific assessments of which countries have the most beautiful women.
While there are at least six different bra-sizing systems in use worldwide (the easiest example being that some countries use inches, such as 34C, and other countries measure in centimeters, such as 70C), bra sizes are generally expressed by cup sizes.
As a rule, the number represents the horizontal measurement around the "band" or “underbust" area just underneath the breasts. To determine cup size, fitters measure around the fullest part of the breast (typically in line with the nipples) and compare that to the underbust. The greater the difference between these measurements, the larger the cup size. These measurements are usually expressed in letters, with A cups being the smallest and moving upward through the alphabet to D (or higher) from there.
It is important to remember that not all sizes within a given cup size will be the same. For example, a 32C is much smaller in volume than a 42C because there is a greater difference in the band size and fullest part of the breast measurements.
Finally, bra sizes may differ from one manufacturer to another even in the same country. As such, instead of simply assuming that a new 34B (for example) in one brand will match the 34B one is already wearing from another brand, it is wise to know one's measurements in inches and look up the corresponding size on the new bra maker's chart.
With all these differences in mind, the way researchers determine the average breast size in a country is to examine the sales numbers for the various sizes of bra being sold. While not all C cup breasts will be the same size (even if they have the same band size) it is really the cup size that is being tracked and not the size of the actual breasts.
The most comprehensive available data on breast size around the globe indicates that the average cup size varies from a low of AA to a high of C, depending upon the country.
It is noteworthy that breast size correlates quite closely with overall BMI, illustrating the fact that additional weight can often be accompanied by a larger cup size.
Also notable is the fact that this data set does not include every country in the world. For example, Norway was left out of the data set, so it does not appear. If it did, it could possibly appear alongside fellow Nordic countries Sweden, the Netherlands, and Switzerland in the top 10.
Overall, the largest breast sizes are concentrated in Europe and the United States. The smallest breast sizes are concentrated in African and southeast Asian countries. Experts suggest this is due largely to both genetics, as the women in these regions tend to be smaller overall, and to the fact that the women of these areas often live more active lifestyles, which can decrease both body mass and breast size.
Average Cup Size
The United States and the United Kingdom both have average bra sizes of a C cup.
Twenty-three countries have very small breast sizes. The following are some of the nations with average cup sizes of AA: Bahamas, Gambia, Mongolia, Lebanon, Kyrgyzstan, Laos, Tunisia, and Burundi.