Bra Equivalents: Sister Sizes for 34f, 34g, 36ddd, 38dd, 38ddd, 40dddd

If your current bra doesn’t seem the right fit, the problem doesn’t always have to be the brand. 8 out of 10 women are found to be wearing the wrong size for their body. This might seem like a shocking statistic, but it’s not surprising once you consider that women barely know how to check for the right fit.

Here we bring you a guide to finding the right fit as well as a groundbreaking solution: bra sister sizes. Find out all the bra equivalent sister sizes for 34f, 34g, 36ddd, 38ddd, and 40dddd.


You can choose a different size than you’re used to as long as they have roughly the same measurements. Here is what you need to know.

  • The bra sister size equivalents for 34F are 32FF and 36E.
  • The bra sister size equivalents for 34G are 32G and 36F.
  • The bra sister size equivalents for 36DDD are 34F and 38DD.
  • The bra sister size equivalents for 38DD are 36DDD and 40D.
  • The bra sister size equivalents for 38DDD are 36F and 40DD.
  • The bra sister size equivalents for 40DDDD are 38F, 40E, & 42DD.
34d bra

Table of Contents

What are bra sister sizes?

If your cups fit well, but something still feels off, sister sizes might be worth considering. These complimentary sizes are near your current size but might fit you better than your everyday bra.

Going up in sister sizes means increasing the band but reducing the cup letter. Going down means reducing the band but increasing the letter.

However, if you find yourself in a bra that your breasts are spilling out of, it is time to go in for a fitting. It’s no different from wearing the right shirt!

red bra

34b, 34c, 34d, 34dd, 34f, 34g, & 34h bra sister size equivalents

DownCurrent ‘‘Up

If your 34B isn’t doing you good, then:

Size up to a 36A: This will offer you a more comfortable fit than a 34B, given its two more inches of the band.

Go down to 32C: It will be tight around your body, with the same cup.

If you’re a 34C, your sister’s bra choices are

Size up to 36C: It does you more good with the extra room than a 34C but the same comfort when it comes to the cups.

Go down to a 32D: A more tight fit around the body. For someone who found a 36 dangling on their body.

The sister sizes for 34D

34d bra

Try a 36C: If you feel a 34D is too ill-fitting and digs into the skin, a 36C gives you more room.

Go down to a 32DD: A 32DD offers a more body-hugging fit within the same cup.

A 34DD? Then you can

Try a 36D: It gives you the comfort of the same cup but a 2-inch bigger band.

Go down to a 32DDD/32E: It gives you the comfort of the same cup but 2 inches smaller band.

Is a 34F too ill-fitting for you?

Size up to 36E: Get relief from a 34F digging into your skin with 2 inches more in the band.

Go down to a 32FF: Get more support than a 34F with a decrease in 2 inches band.

If your 34G doesn’t do you much good

Go up to a 36FF: Offers you relief from a 34G if you feel it’s too small for you. Nonetheless, the cup is the same.

Go down to a 32GG: Hug your frame 2 inches more than a 34G.

Sister bras for your 34H

Go up to a 36GG: Looser than a 34H fitting within the same cup.

Go down to a 32HH: Feel too small for a 34H? A 32HH will offer you a smaller fit in the same cup.

36b, 36c, 36d, 36dd, 36f, 36ddd, & 36g bra sister size equivalents


At present, if you aren’t finding your 36B of the perfect fitting, you can,

Try a 38A: A will hug you 2 inches looser than a 36B, and the cup remains the same.

Go down to a 34C: A 34C will hug you 2 inches tighter than a 36B without a change in the cup.

If you’re a 36C but aren’t quite sure about it

Go up to a 38B: Without altering the size of your current cup, you can expand the band around your torso by two inches.

Go down to a 34D: You feel that the cups finally hug you just right, but the bra could overall be more close-fitting? Then a 34D is two inches smaller overall without any change in a cup.

If you’re a 36D and not happy with the fit

36d bra

Go up to 38C: The back is 2 inches wider without changing the cup.

Go down to a 34DD: The back of the bra is 2 inches lesser in circumference, making it more close-fitting than a 36D.

If you’re a 36DD and don’t think it’s your ideal bra

Go up to a 38D: It’s 2 inches bigger around your body, but the cup is the same.

Go down to a 34DDD/34E: It’s a closer-fitting bra that hugs you 2 inches more than a 36DD.

If you feel that a 36F isn’t doing you much good

Go up to 38E: This will give you more room for your body to breathe as it’s 2 inches broader, while the cups will be the same as a 26F.

Go down to 34FF: A 34FF bra is 2 inches more figure-hugging than a 36F. Although, the cups are the same as 36F.

If your 36DDD doesn’t feel right

Go up to a 38DD: With cups the same, it’ll give you 2 inches more space than a 36DDD.

Go down to a 34F: Get 2 inches cozier of a fit than a 36DDD and the same cup.

If your 36G bra isn’t doing you good,

Try a 38FF: It’ll give you 2 inches more breathing space while the cups remain the same.

Go down to a 34GG: Get 2 inches of a more secure fit around your body within the same cup.

38a, 38b, 38c, 38d, 38dd, 38ddd, 38f, 38g bra sister size equivalents


Are you a 38A? Here are sister bra sizes you can try

Size up to a 40AA: A more oversized fit than the 38A but with the same cup.

Go down to a 36B: A smaller fit than the 38A, but with the same cup.

Is your 38B not giving you the same comfort?

Try a 40A: If a 38B is too tight, 40A will be a more relaxed fit with the same cup.

Go down to a 36C: The same cup as a 38B but is more hugging than a 38B.

Not happy with your 38C fitting?

Size up to a 40C: Within the same cup, it offers 2 inches of more freedom than a 38C

Go down to a 36D: Within the same cup, it gives 2 inches more support by being tight around your body.

Given your 38D isn’t doing good for you.

38d bra

Size up to a 40C: More relaxed around the torso, but the same cup as a 38D

Go down to a 36DD: If a 38D were barely hanging on, 36DD would give more support within the same cup.

Is a 38DD too uncomfortable of a fit?

Try a 40D: If a 38DD is too tight, you will be more at ease wearing a 40D.

Go down to a 36DDD/36E: Closer-fitting band around your torso with the comfort of the cups, which remain the same as 38DD

Are you a 38DDD? Here are your sister sizes:

Try a 40DD: For a bra that’s looser than a 38DDD but offers the same cup.

Go down to 36F: For a bra that’s tighter than a 38DDD but within the same cup.

38F fitted bra, doesn’t feel right to you?

Size up to a 40E: If a 38F bra is too tight for you, but the cup is accurate.

Go down to a 36FF: If a 38F bra is slightly hanging on you, but the cup is perfect.

If you wear a 38G, for a better you can

Size up to a 40FF: Perfect if a 38G is too tight around your frame.

Go down to a 36GG: Ideal if a 38G is too loose around your frame, but it is the perfect cup for you.

40b, 40d, 40dd, 40ddd, 40h bra sister size equivalents


If your 40B bra isn’t satisfactory

Try a 42A: For an extended band length but same cup comfort.

Go down to a 38C: For someone with a narrow body frame but needs the same comfort as a 40B.

A 40D can feel uncomfortable to some.

40d bra

Try a 42C: A 42C is great for people who feel grown out of their 40D bra but not its cup.

Go down to a 38DD: A notable improvement for somebody who finds a 40D too big for them, but its cup is a great fit.

A 40DD isn’t your ideal fit?

Try a 42D: The band of a 42D is larger than a 40DD, while the cup is not.

Go down to a 38DDD/38E: For petite people who’d like a more snug fit of the 40DD.

If you’re a 40DDD but not happy with it

Try a 42DD: A 42DD will give you more room around your body than a 40DDD if you need it.

Go down to 38F: A 38F will provide a more compact fit than a 40DDD with the same comfort of the cups.

If 40H isn’t doing you justice, then:

Try a 42GG: More comfortable if a 40H is giving too much compression to your body.

Go down to a 38HH: Great if the 40H isn’t giving as much compression as it should to give ideal support.

Best brands

When it comes to the best brands, here are some of our recommendations:

  • Calvin Klein
  • Hanky Panky
  • ThirdLove
  • Victoria’s Secret
  • Cuup

When it comes to sports bras, these are our brand recommendations:

  • Nike
  • Lululemon
  • Girlfriend Collective

42b, 42c, 42d, 42ddd, 42f & 42g bra sister size equivalents


42B? but not sure if it’s the correct fit for you?

Try a 44A: A decent difference in circumference of a 42B with the same cup.

Go down to a 40D: A significant decrease in circumference from a 42B but with the same cup.

Sure, of the 42C cup size but not the band?

Try a 44B: Giving you the comfort of a 42B with the extended band.

Go down to 40D: It provides an easy transition from a 42C with a more figure-hugging fit.

If the 42D isn’t right for you

Try a 44C: Providing you more room between the bra and your body than 42D, without a change in the cup.

Go down to a 40DD: The bra hugs you tighter than a 42D with the same comfort.

Is a 42DDD rather uncomfortable for you?

Try a 44DD: Offering you a slight breather than a 42DDD, which might have been too tight.

Go down to a 40F: Supporting you a little extra with its smaller band.

Sure, of 42F, but not the band size?

Try a 44E: Same cups but an overall bigger bra for utmost comfort.

Go down to 40FF: For somebody who’s too petite for a 42F but requires the same comfort.

Is your 42G not as comfortable as you’d like?

Try a 44FF: If you feel a 42G offers the ideal cup but digs into your skin.

Go down to 40GG: If you feel 42G is too limp on you.

Best places to buy them

If you’re looking for a place to buy them, here’s a list of places we suggest:

  • Amazon
  • Soma
  • Knix
  • Nordstrom
  • Bare necessities


pink bra

Here are some of our answers to customers more burning questions.

Do bra sister sizes work?

Bra sister sizes are revolutionary for women who are unaware of the concept. You can go up or down according to your needs. You can sister size again if need be.

But it’s worth noting that if you sister size repeatedly, you can end up with the totally wrong fit for your body in the end. This is because the bra is nothing like the original you started with by the end of this exercise.

How should a bra fit?

Next time you go shopping, you can keep these pointers in mind:
– The loosest hook should also be comfortable and snug. As the band stretches out with use, you’ll be able to use the other hooks too.
– Your entire breast should be held within the cup. This ensures maximum support.
– Your straps moving around should not affect you. Even if you move around the straps an inch here and there, the fit should not be affected.
– Your breasts should not be spilling out towards your armpits or be pushed and spilling out from the middle.

Is a DDD cup the same as an F?

Yes. A DDD is the same as an F in full-figure bras. In full-figure bras, the DD is equivalent to an E. The labeling will vary from brand to brand.

How do I know my sister size?

If your cups are ill-fitting, you need to go for a bra fitting session to know your size truly. However, if they fit fine, take a look below at some pointers you should know:
– If you wear your bra on the tightest possible hook, your sister size down might work better for you! A sister size down means one letter name larger and one band smaller than your current. Like a 34C will be sized down to 32D.
– If you wear it on the loosest hook possible, you might need to sister size up! So if you have a 30D, you’ll try a 32C.

When is sister sizing useful?

– Your straps keep falling off, and it’s embarrassing. You think the fit is ok, but it is probably a tad loose on some parts and tight on others.
– You are suffocating in the bands on your chest because the fit is too tight. But you think the cups fit well, so you continue to suffer in silence.
– Your brand doesn’t make the one you want any larger than you’d like. Sometimes you need a 42DD, but the brand stops at a 42D.
All these reasons are more than enough to go for sister sizing.