Bra Knowledge » How bra sizes work » Versions » How bra sizes work as of 2015-09-19 01:37:40.435702
When talking about bra sizes, we will be referring about bras that use letter and numbers for sizing. Usually start with a number followed by a letter, a few examples:
- 34B
- 36DD
- 28G
- 40E
The number indicates the band size of a bra. This makes reference to your the size of your torso/ribcage right below your breasts. The numbers used can vary between regions or brands. The above examples use US/UK sizing (based on inches).
The letters are used to determine the cup size of the bra. This is relates to the breast mass, colloquially, "how big" your boobs are. The farther along in the alphabet, the bigger the cup. The way that the cup letters go up will vary between brands, some brands will use cups DDD, others will use E cups and so on (this makes things complicated on bigger sizes).
The letter to use indicates how much bigger the full bust measurement is with respect to the band size. This means that the band size and the cup size are dependent of each other so a cup size is always needs a band size to indicate how big or small breasts are. There is no "D" cup, since it will fit very different breasts in a 28 band than in a 40 band.
Band size
The band size is determined by a number which is related to the circumference of your torso.
Most bands will measure, in inches, a bit less than the size they are, but stretch past that number. For example, a 32 band might measure 28 inches unstretched, and stretch to 35 inches. Different brands and styles may have more or less stretchy bands.
Most women find that the best fit is the band size closest to their underbust measurement (in inches). The best fitting band size will depend on how squishy your tissue is where the band sits, and the weight of your breasts. There is some amount of personal preference involved in this too, as some women find they like a firmer band and some like the band to be a bit looser.
Adding inches to your torso to calculate your band size
Early bras were produced before elastic material and, for some reason, the old measurement tables are still being used in some places, even though nowadays bra bands are made of elastic material and therefore stretch.
This easily explains why the +4/+5-sizing method doesn’t work very well if you want your bra band to support you: the band stretches out too much! You can test that by stretching out a band from a +4/+5-fitted bra - they will often stretch absurdly far.
Cup size
The cup size is a letter which is determined by the difference between the full-bust and the band measurement.
A cup size always depends on the band length! You can't only say "I wear a D-cup" because a 34D and a 42D are totally different sizes!
A person who wears a bra in the size 34D has a smaller breast circumference than a person who wears a bra in the size 42D. Because cup size is relative to the band size, all this means is that they have the same difference between their breast circumference and the band length.
See these resources to read more about this:
You may find that in order to have a bra band that supports you, you have to choose a band length that sounds much smaller than what you have been used to. If you are going to look at a bra with a smaller band, then the cup size will have to change as well. If you used to wear a bra in the size 34C and find that a band length of 30 fits you much better, you would have to wear a 30DD to have the same cup size as before. (also see the following section sister sizes)
Sample bra sizes table
Sister sizes
Two sizes are considered sister sizes when their bands are consecutive but their cups maintain a similar fit. Usually, a sister size is found when adding or subtracting one cup when going up or down one band size.
This can be explained when you consider that a cup size is always determined by a difference between band and full-bust measurement.
Different sizing systems
There are a lot of different bra sizing systems, some of which can be converted to other systems and some of which cannot. Sometimes the sizing systems are applied consistently or they might vary between brands or even models of one brand!
Check Bra Fitting Cidade for an overview of the most common sizing systems.
Size range available
The actual size range available might be much bigger than you imagine. On Bratabase, bras in sizes from 26D to 50N have been added and this size spectrum is ever expanding!
On bra models which have been added to Bratabase there's a field which shows you in which sizes this bra is being made.
Calculators
There are a number of different bra size calculators on the web. Try for example the bra calculator on Sophisticated Pair. It can give you an idea of where to start when you want to try out a new size. (You should probably choose the loose band setting if you're new to bra-fitting. You can always try on shorter bands if they don't feel snug enough.) Please don't give up immediately if the recommended sizes sound really odd and way too big - don't be a victim of letterphobia. :)
Keep in mind though: A calculator can always only give you an idea. It never says the whole truth, a lot of us need different sizes in different brands or on different parts of our menstrual cycle.
Check the article on right fit of bras to find out how to tell if your bra fits, and how to find a better size if it doesn't.
Resources and further reading
- On Wikipedia: Bra measurements for a historical overview, bra size standards and further information.