Do Sister Sizes Really Work? Do They Fit the Same?

Do Sister Sizes Really Work? Do They Fit the Same?

Do sister sizes really work? Do the bras really fit the same? In this guide, you’ll find out when sizing up or down is recommended and whether the new sizes will fit the same.

Most women have a love-hate relationship with their bras. The undergarment is sometimes unpleasant but you definitely need them in your collection. However, there’s no medical or scientific reason for wearing, bras save for after a cosmetic surgery or when exercising.

Regardless, bra shopping should be a fun experience as the nicknames suggest, but it’s not! Fortunately, there are some tricks that will see you through the process. For instance, you probably could wear three different sizes with a perfect fit – the actual size and its sister sizes.

Confusing, right?

Let’s get into the details:

Sister sizes typically mean the bras have similar cup volumes. The only difference is in the band sizes. So, practically, you can swap the sister size with your actual size and the fit will still be perfect. However, you’ll have a problem with the band as it will either fit looser or tighter than normal.

How to Find Your Sister Size

When going down a sister size, increase the cup size and reduce the band size. For instance, if your bra size is 34C, then 32D would be your ideal sister size on the lower side.

The same applies when trying to find a higher sister size – size down the cup while going up a band size. In this scenario, 36B it is! See? Easy-peasy!

Check the sister size chart below for bras that have the same cup size:

Bra Sister Sizes

30 32 34 36 38 40 42 44 46 48
30B 32A 34AA
30C 32B 34A
30C 1/2 32B 1/2 34A 1/2
30D 32C 34B 36A
30D 1/2 32C 1/2 34B 1/2 36A 1/2
30E (DD) 32D 34C 36B 38A
30E 1/2 32D 1/2 34C 1/2 36B 1/2 38A 1/2
30F (DDD) 32E (DD) 34D 36C 38B 40A
32E 1/2 34D 1/2 36C 1/2 38B 1/2 40A 1/2
30G (DDDD) 32F (DDD) 34E (DD) 36D 38C 40B
32G (DDDD) 34F (DDD) 36E (DD) 38D 40C 42B
32H 34G (DDDD) 36F (DDD) 38E (DD) 40D 42C 44B
34H 36G (DDDD) 38F (DDD) 40E (DD) 42D 44C 46B
36H 38G (DDDD) 40F (DDD) 42E (DD) 44D 46C 48B
38H 40G (DDDD) 42F (DDD) 44E(DD) 46D 48C
38I 40H 42G (DDDD) 44F (DDD) 46E(DD) 48D

Do Sister Sizes Really Work?

So sister sizes really work? If so, how?

Determining your actual size will help you understand how sister sizing really works. The exercise requires some mathematics and measuring.

Use a tape measure to determine the length around the ribcage where the bra band usually sits to get your accurate band size. The figure should be an even number, if not, round it off to the nearest one and bingo! That is one half of the size already.

To get your cup size, use the tape to determine the circumference of your chest at the fullest part of the breasts. Again, round off the figure to the nearest even number and get the difference. The cup size is the sum difference between the band size and bust line measurement. An inch is A Cup, two for B, three for C and so fourth.

The band and cup size are not standard numbers on their own but directly relate. In layman terms, different cups may have different letters. For instance, 40D breasts are bigger than 30D breasts. It also means different cup and band combinations can have a similar cup volume.

Do Sister Sizes Fit the same as Your Actual Size?

Absolutely not! However, they come in handy if you looking for a tighter or looser band fit as you only need to go for a different cup size. Besides, if you can’t get your favorite lingerie in your actual size, you can always size up or down as per your preferences. Sister sizing will also help you find a bra with a perfect fit especially when shopping for a new brand.

What’s more, with sister sizing, you might actually realize you have been wearing an ill-fitting bra unknowingly for the longest time! Try a sister size for a change if you notice your bra has a loose fit. You might realize it offers better support and has a great fit. You can’t know what you are missing unless you give it a try!


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