Sister size

A woman compares two sister sizes to her correctly-fitting bra (right).

Sister sizes always have the same cup volume as each other.

A sister size is a related bra size with the same cup volume of each other. One's sister size could, in theory, be used as a substitute for one's true size, but the bra wouldn't fit correctly.

Theory

This illustration compares breast volumes. Listed volumes are volume per breast.

Sister sizes have the same cup volume as each other. The difference of band size simply changes the fit. The idea behind sister sizes: If you increase the band size, you need to decrease the cup size to maintain the same volume. If you decrease the band size, you will need to increase the cup size therefore.

Typical stores suggest sister sizes to sell their limited inventory to the customer, as opposed to a bra that actually fits. This perpetuates the problem of most women wearing band sizes too large, with correspondingly wrong cup sizes.

Sometimes, two adjacent sister sizes may both fit a woman, since the cup volume is the same, while the band size can be adjusted to a small degree by using the hook and eye fasteners in the bra clasp. However, it is usually less comfortable and flattering.

Charts

Main article: Bra sizing by country

UK sister sizes

Sister sizes (UK sizing)

26	28	30	32	34	36	38	40	42	44	46	48	50	52	54
26AA
26A	28AA
26B	28A	30AA
26C	28B	30A	32AA
26D	28C	30B	32A	34AA
26DD	28D	30C	32B	34A	36AA
26E	28DD	30D	32C	34B	36A	38AA
26F	28E	30DD	32D	34C	36B	38A	40AA
26FF	28F	30E	32DD	34D	36C	38B	40A	42AA
26G	28FF	30F	32E	34DD	36D	38C	40B	42A	44AA
26GG	28G	30FF	32F	34E	36DD	38D	40C	42B	44A	46AA
26H	28GG	30G	32FF	34F	36E	38DD	40D	42C	44B	46A	48AA
26HH	28H	30GG	32G	34FF	36F	38E	40DD	42D	44C	46B	48A	50AA
26J	28HH	30H	32GG	34G	36FF	38F	40E	42DD	44D	46C	48B	50A	52AA
26JJ	28J	30HH	32H	34GG	36G	38FF	40F	42E	44DD	46D	48C	50B	52A	54AA
26K	28JJ	30J	32HH	34H	36GG	38G	40FF	42F	44E	46DD	48D	50C	52B	54A
26KK	28K	30JJ	32J	34HH	36H	38GG	40G	42FF	44F	46E	48DD	50D	52C	54B
26L	28KK	30K	32JJ	34J	36HH	38H	40GG	42G	44FF	46F	48E	50DD	52D	54C
26LL	28L	30KK	32K	34JJ	36J	38HH	40H	42GG	44G	46FF	48F	50E	52DD	54D
26M	28LL	30L	32KK	34K	36JJ	38J	40HH	42H	44GG	46G	48FF	50F	52E	54DD
26MM	28M	30LL	32L	34KK	36K	38JJ	40J	42HH	44H	46GG	48G	50FF	52F	54E
26N	28MM	30M	32LL	34L	36KK	38K	40JJ	42J	44HH	46H	48GG	50G	52FF	54F
	28N	30MM	32M	34LL	36L	38KK	40K	42JJ	44J	46HH	48H	50GG	52G	54FF
		30N	32MM	34M	36LL	38L	40KK	42K	44JJ	46J	48HH	50H	52GG	54G
			32N	34MM	36M	38LL	40L	42KK	44K	46JJ	48J	50HH	52H	54GG
				34N	36MM	38M	40LL	42L	44KK	46K	48JJ	50J	52HH	54H
					36N	38MM	40M	42LL	44L	46KK	48K	50JJ	52J	54HH
						38N	40MM	42M	44LL	46L	48KK	50K	52JJ	54J
							40N	42MM	44M	46LL	48L	50KK	52K	54JJ
								42N	44MM	46M	48LL	50L	52KK	54K
									44N	46MM	48M	50LL	52L	54KK
										46N	48MM	50M	52LL	54L
											48N	50MM	52M	54LL
												50N	52MM	54M
													52N	54MM
														54N

US sister sizes

Sister sizes (US sizing)

28	30	32	34	36	38	40	42	44	46	48	50	52	54	56	58
28AA
28A	30AA
28B	30A	32AA
28C	30B	32A	34AA
28D	30C	32B	34A	36AA
28DD/E	30D	32C	34B	36A	37AA
28DDD/F	30DD/E	32D	34C	36B	38A	40AA
28DDDD/G	30DDD/F	32DD/E	34D	36C	38B	40A	42AA
28H	30DDDD/G	32DDD/F	34DD/E	36D	38C	40B	42A	44AA
28I	30H	32DDDD/G	34DDD/F	36DD/E	38D	40C	42B	44A	46AA
28J	30I	32H	34DDDD/G	36DDD/F	38DD/E	40D	42C	44B	46A	48AA
28K	30J	32I	34H	36DDDD/G	38DDD/F	40DD/E	42D	44C	46B	48A	50AA
28L	30K	32J	34I	36H	38DDDD/G	40DDD/F	42DD/E	44D	46C	48B	50A	52AA
28M	30L	32K	34J	36I	38H	40DDDD/G	42DDD/F	44DD/E	46D	48C	50B	52A	54AA
28N	30M	32L	34K	36J	38I	40H	42DDDD/G	44DDD/F	46DD/E	48D	50C	52B	54A	56AA
	30N	32M	34L	36K	38J	40I	42H	44DDDD/G	46DDD/F	48DD/E	50D	52C	54B	56A	58AA
		32N	34M	36L	38K	40J	42I	44H	46DDDD/G	48DDD/F	50DD/E	52D	54C	56B	58A
			34N	36M	38L	40K	42J	44I	46H	48DDDD/G	50DDD/F	52DD/E	54D	56C	58B
				36N	38M	40L	42K	44J	46I	48H	50DDDD/G	52DDD/F	54DD/E	56D	58C
					38N	40M	42L	44K	46J	48I	50H	52DDDD/G	54DDD/F	56DD/E	58D
						40N	42M	44L	46K	48J	50I	52H	54DDDD/G	56DDD/F	58DD/F
							42N	44M	46L	48K	50J	52I	54H	56DDDD/G	58DDD/F
								44N	46M	48L	50K	52J	54I	56H	58DDDD/G
									46N	48M	50L	52K	54J	56I	58H
										48N	50M	52L	54K	56J	58I
											50N	52M	54L	56K	58J
												52N	54M	56L	58K
													54N	56M	58L
														56N	58M
															58N

Benefits

For people whose ideal bra size is somewhat of an outlier, like 28C or 36L, using a sister size (often a larger band/smaller cup) can allow the person to wear a particular bra that is otherwise off-limits to them due to being outsized. For example, someone who needs a 28C can try 30Bs to expand their selection of bra styles. They could then alter the band or use a Rixie Clip to make the bra fit better.

Some brands, or particular styles from some brands, can run smaller or larger than another bra of the same size. Because of this, someone who wears a size right outside the bra's size range could end up fitting into it because the bra band might run a little small or the cup might run big and vice versa.

These bras all hold the same volume, but their proportions are very different.

Dangers

It is not recommended to wear a bra any more than one sister size away from your ideal bra size. This is because, while, for example, sister sizes 34FF, 36F, 38E, 40DD, and 42D all hold the same volume, the bras are designed for very different body shapes. The higher in band/lower in cup you go, the shallower and wider the cup becomes. If the bra band is altered to be smaller, the way the cup fits will change and the straps also start out further. The lower in band/higher in cup you go, the more projected and narrow the cups get. The more extenders used, the further out the straps lay, which can cause them to constantly slide off your shoulders as they now sit closer to the arms rather than the shoulder blade.

See also

• Bra-fitting method
• Bra sizing by country
• How-to bra shop

External Links

• Sister Size India