Bra Sister Size Calculator

Never let the assumption of not finding your bra size overwhelm you. You could get your bra sister size!

Bra sister sizes are lifesavers when it comes to women’s underwear.  When buying a bra, you might encounter the problem of a smaller or bigger cup. That’s where your bra sister size comes in and saves the day! 

With the great importance of knowing your sister’s size, we present the bra sister size calculator. 

This Bra Sister Size Calculator gets you prepared when going bra shopping. This means you can easily get other options that fit you and can serve as a substitute for your actual bra size. 

Ready to find out your bra sister sizes? Let’s take the lead. 

Bra Sister Size Chart US Sizing

What does the Bra Sister Size Calculator do?

There are several Bra Sister Sizes Charts across the web with different International Standards and this makes it complicated to understand your sister sizes. The bra sister size calculator on the other hand gives you an easy way to calculate your sister sizes and saves you the stress of looking through some difficult tables. 

To calculate your sister size, you only need to select your bust size and your cup size. Boom! The calculator tells you the exact Bra Sister Sizes to the one you have selected. 

For instance, if your bust size is 30, simply input it and select your cup size (from AA-J) and the calculator tells you your sister size options. 

If you do not know how to get your cup size, simply check out our Bra size calculator to determine your cup size for you.

What are Bra Sister Sizes?

The bra sister sizes act more like companions to your bra size. They are a group of bra sizes that have the same cup volume but different band sizes. For example, a 34C and a 36B have the same cup volume but different band sizes.

This means, there are choices to select from in a bra store. So, when your actual bra size is not available, you can simply go downwards on band size or go upwards on a cup size or vice versa. 

What determines your bra sister sizes? 

Your sister sizes are determined by your bust and band measurements. The bust measurement is taken around the fullest part of your bust and your band measurement is around your ribcage which is under your bust. The difference between the two gives you your cup size. So if your bust size is 36 and your band measurement is 32, the difference gives you your cup size. 

Your cup size determines your bra sister sizes. These are the sizes before and after your bra size. Despite this, there are cases where you need to go upwards or downwards depending on the cup volume and band measurement of the bra. 

Here are a few options for the different bra sizes:

 34B could be sized down to 32C and sized up to a 36A

A 36C could be sized down to a 34D and sized up to a and a 38B

A 38D could be sized down to a 36DD and a 40C

What units does this Bra Sister Size Calculator use in calculating?

The bra sister size calculator uses three different units: UK, US, and EU. 

These units represent the different measurement systems used in different countries, and it’s important to know which one to use to get the most accurate results.

UK/US Units

The UK unit of measurement is used in the United Kingdom, and it’s based on inches. This means that the measurements used in the calculator will be in inches if you select the UK unit.

The US unit of measurement is used in the United States, and it’s also based on inches. This means that the measurements used in the calculator will be in inches if you select the US unit.

EU (European Union) Units

The EU unit of measurement is used in European countries, and it’s based on centimeters. So, if you pick EU, the calculator will be in centimeters. 

When you’re using a bra sister size calculator, make sure you select the right unit of measurement based on where you’re located. This will ensure that you get the most accurate results and find the perfect bra size for you.

How to calculate your Bra Sister Size manually?

Calculating your bra size manually can be stressful and confusing. However, the simplest way to calculate your sister size is to know your bra size and cup size.  Once you know them, it becomes easy to use a Bra Sister Size Calculator.

To know your actual size, get a measuring tape and measure your bust and band measurements. Basically, the fullest part of your bust and your ribcage which is under your bust.

While measuring, make sure the tape is not too tight or too loose on you. 

Got your results? Jot them down and subtract the band size from the bust size. The answer is your cup size. 

Once you know your cup size, you can find your bra sister size. If you want to go up a band size and go down a cup size (this happens in cases the band is too tight), you can subtract one from your band size and add one to your cup size. For example, if your current size is 34B, your sister size should be 32C.

While a 32C should fit, every brand and style may fit differently. So try on your sister size and see how they feel. 

Why is it important to Know your Bra Sister’s Size? 

We could say not going home disappointed from a store. 

That could be it. 

However, many women struggle with finding bras that fit comfortably and provide the right amount of support. One of the biggest reasons for this is not knowing their sister size. To solve this? 

It might simply be that you need a different size that is equivalent to your current size but with a different cup or band measurement.

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This makes it important to know your bra sister sizes cause every bra size has a sister size, and this knowledge provides you with available options and better fit in cases of larger or smaller cups or bands. 

Frequently Asked Questions about Bra Sister Sizes

We’ve guessed that there might be some unanswered questions and hope to answer them in this section.

1. Can I go for my bra sister size?

Sure! If your bra size is not available in a store, you can check out your sister sizes for preferable options. 

2. How accurate are sister sizes?

Sister sizes are not the perfect fit for you. Your bra size is. Nonetheless, sister sizes can provide and give you the support you need most times in cases of brand sizing.   

3. How do I find my Sister size?

You can find your sister size by moving one band size up and one cup size down or one band size down and one cup size up. For example, if you wear a 34C, your sister sizes would be a 36B and a 32D.

4. What are the benefits of wearing a sister size?

Wearing a sister size can help you find a better fit if your regular size is uncomfortable or if your bra is not providing enough support. It can also be helpful if your regular size is out of stock or unavailable.

5. How do I know if a sister size is not the right fit?

If the band is too tight or the cups are too small or too large, the sister size may not be the right fit. It’s important to try the bra on and ensure that it fits well and provides the necessary support.

6. Is it possible to wear a sister size for a longer period of time?

It is possible, but it is important to make sure that the fit is comfortable and provides the necessary support. It may be necessary to make adjustments to the band size or straps to ensure a proper fit.

7. Can I wear a sister size if I am between sizes?

Yes, you can wear a sister size if you are between sizes. It can help you find a better fit if your regular size is uncomfortable or if your bra is not providing enough support.

8. Will my Sister size be the same for all brands of bras?

No, the sister size may vary depending on the brand of bra. Therefore, it’s a good idea to check the sister size chart provided by the brand or try different sizes to find the right fit.

9. Can I wear a sister size if I have a small bust?

Yes, you can wear a sister size if you have a small bust. It can help you find a better fit and ensure that the bra provides the necessary support.

10. Can I wear a sister size if I have a large bust?

Yes, you can wear a sister size if you have a large bust. It can help you find a better fit and ensure that the bra provides the necessary support.

11. Will my sister size change if I gain or lose weight?

Yes, your sister size may change if you gain or lose weight. It is important to periodically check your fit and make adjustments as necessary.

12. Can I wear a sister size if I am pregnant?

Yes, you can wear a sister size if you are pregnant. It can help you find a better fit and ensure that the bra provides the necessary support during this time.

13. Can I wear a sister size if I am breastfeeding?

Yes, you can wear a sister size if you are breastfeeding. It can help you find a better fit and ensure that the bra provides the necessary support during this time.

14. Can I wear a sister size if I have had breast surgery?

It is best to consult with your surgeon before wearing a sister size if you have had breast surgery

Here’s What We Think

Many situations warrant knowing your bra sister sizes. These situations can be avoided and dealt with by calculating your sister sizes. 

If you are in the store and ready to make a purchase, it’s still not late, make use of our bra sister size calculator for other available options. Apart from the Bra Sister Calculator, you can also make use of our Bra Size Calculator to know what your actual Bra Size is. We also have a Bra Sister Converter that can help you convert your Bra Size from one unit to the other.

UK/US Bra Sister Sizes

30 Bust Bra Sister Sizes

1. 30AA Sister Size is 30AA.
2. 30A Sister Size is 32AA.
3. 30B Sister Size is 32A and 34AA.
4. 30C Sister Size is 32B, 34A, and 36AA.
5. 30D Sister Size is 32C, 34B, 36A and 38AA.
6. 30DD Sister Size is 32D, 34C, 36B, 38A and 40AA.
7. 30E Sister Size is 32DD, 34D, 36C, 38B, 40A and 42AA.
8. 30F Sister Size is 32E, 34DD, 36D, 38C, 40B, 42A and 44AA.
9. 30G Sister Size is 32F, 34E, 36DD, 38D, 40C, 42B and 44A.
10. 30H Sister Size is 32G, 34F, 36E, 38DD, 40D, 42C and 44B.
11. 30I Sister Size is 32H, 34G, 36F, 38E, 40DD, 42D and 44C.
12. 30J Sister Size is 32I, 34H, 36G, 38F, 40E, 42DD and 44D.

32 Bust Bra Sister Sizes

1. 32AA Sister Size is 30AA.
2. 32A Sister Size is 30B and 34AA.
3. 32B Sister Size is 30C, 34A and 36AA.
4. 32C Sister Size is 30D, 34B, 36A and 38AA.
5. 32D Sister Size is 30DD, 34C, 36B, 38A and 40AA.
6. 32DD Sister Size is 30E, 34D, 36C, 38B, 40A and 42AA.
7. 32E Sister Size is 30F, 34DD, 36D, 38C, 40B, 42A and 44AA.
8. 32F Sister Size is 30F, 34DD, 36D, 38C, 40B, 42A and 44A.
9. 32G Sister Size is 30H, 34F, 36E, 38DD, 40D, 42C and 44B.
10. 32H Sister Size is 30I, 34G, 36F, 38E, 40DD, 42D and 44C.
11. 32I Sister Size is 30J, 34H, 36G, 38F, 40E, 42DD and 44D.
12. 32J Sister Size is 34I, 36H, 36G, 38G, 40F, 42E and 44DD.

34 Bust Bra Sister Sizes

1. 34AA Sister Size is 30B, and 32A.
2. 34A Sister Size is 30C, 32B and 36AA.
3. 34B Sister Size is 30D, 32C, 36A and 38AA.
4. 34C Sister Size is 30DD, 32D, 36B, 38A and 40AA.
5. 34D Sister Size is 30E, 32DD, 36C, 38B, 40A and 42AA.
6. 34DD Sister Size is 30F, 32E, 36D, 38C, 40B, 42A and 44AA.
7. 34E Sister Size is 30G, 32F, 36DD, 38D, 40C, 42B and 44A.
8. 34F Sister Size is 30H, 32G, 36E, 38DD, 40D, 42C and 44B.
9. 34G Sister Size is 30I, 32H, 36F, 38E, 40DD, 42D and 44C.
10. 34H Sister Size is 30J, 32I, 36G, 38F, 40E, 42DD and 44D.
11. 34I Sister Size is 32J, 36H, 36G, 38G, 40F, 42E and 44DD.
12. 34J Sister Size is 36I, 38H, 40G, 42F & 44E.

36 Bust Bra Sister Sizes

1. 36AA Sister Size is 30C, 32B and 34A.
2. 36A Sister Size is 30D, 32C, 34B and 38AA.
3. 36B Sister Size is 30DD, 32D, 34C, 38A and 40AA.
4. 36C Sister Size is 30E, 32DD, 34D, 38B, 40A and 42AA.
5. 36D Sister Size is 30F, 32E, 34DD, 38C, 40B, 42A and 44AA.
6. 36DD Sister Size is 30G, 32F, 34E, 38D, 40C, 42B and 44A.
7. 36E Sister Size is 30H, 32G, 34F, 38DD, 40D, 42C and 44B.
8. 36F Sister Size is 30I, 32H, 34G, 38E, 40DD, 42D and 44C.
9. 36G Sister Size is 30J, 32I, 34H, 38F, 40E, 42DD and 44D.
10. 36H Sister Size is 32J, 34I, 38G, 40F, 42E and 44DD.
11. 36I Sister Size is 34J, 38H, 40G, 42F & 44E.
12. 36J Sister Size is 38I, 40H, 42G & 44F.

38 Bust Bra Sister Sizes

1. 38AA Sister Size is 30D, 32C, 34B and 36AA.
2. 38A Sister Size is 30DD, 32D, 34C, 36B and 40AA.
3. 38B Sister Size is 30E, 32DD, 34D, 36C, 40A and 42AA.
4. 38C Sister Size is 30F, 32E, 34DD, 36D, 40B, 42A and 44AA.
5. 38D Sister Size is 30G, 32F, 34E, 36DD, 40C, 42B and 44A.
6. 38DD Sister Size is 30H, 32G, 34F, 36E, 40D, 42C and 44B.
7. 38E Sister Size is 30I, 32H, 34G, 36F, 40DD, 42D and 44C.
8. 38F Sister Size is 30J, 32I, 34H, 36G, 40E, 42DD and 44D.
9. 38G Sister Size is 32J, 34I, 36H, 40F, 42E and 44DD.
10. 38H Sister Size is 34J, 36I, 40G, 42F & 44E.
11. 38I Sister Size is 36J, 40H, 42G & 44F.
12. 38J Sister Size is 40I, 42H & 44G.

40 Bust Bra Sister Sizes

1. 40AA Sister Size is 30DD, 32D, 34C and 36B and 38A.
2. 40A Sister Size is 30E, 32DD, 34D, 36C, 38B and 42AA.
3. 40B Sister Size is 30F, 32E, 34DD, 36D, 38C, 42A and 44AA.
4. 40C Sister Size is 30G, 32F, 34E, 36DD, 38D, 42B and 44A.
5. 40D Sister Size is 30H, 32G, 34F, 36E, 38DD, 42C and 44B.
6. 40DD Sister Size is 30I, 32H, 34G, 36F, 38E, 42D and 44C.
7. 40E Sister Size is 30J, 32I, 34H, 36G, 38F, 42DD and 44D.
8. 40F Sister Size is 32J, 34I, 36H, 38G, 42E and 44DD.
9. 40G Sister Size is 34J, 36I, 38H, 42F & 44E.
10. 40H Sister Size is 36J, 38I, 42G & 44F.
11. 40I Sister Size is 38J, 42H & 44G.
12. 40J Sister Size is 42I & 44H.

42 Bust Bra Sister Sizes

1. 42AA Sister Size is 30E, 32DD, 34D, 36C, 38B and 40A.
2. 42A Sister Size is 30F, 32E, 34DD, 36D, 38C, 40B and 44AA.
3. 42B Sister Size is 30G, 32F, 34E, 36DD, 38D, 40C and 44A.
4. 42C Sister Size is 30H, 32G, 34F, 36E, 38DD, 40D and 44B.
5. 42D Sister Size is 30I, 32H, 34G, 36F, 38E, 40DD and 44C.
6. 42DD Sister Size is 30J, 32I, 34H, 36G, 38F, 40E and 44D.
7. 42E Sister Size is 32J, 34I, 36H, 38G, 40F and 44DD.
8. 42F Sister Size is 34J, 36I, 38H, 40G & 44E.
9. 42G Sister Size is 36J, 38I, 40H & 44F.
10. 42H Sister Size is 38J, 40I & 44G.
11. 42I Sister Size is 40J & 44H.
12. 42J Sister Size is 44I.

44 Bust Bra Sister Sizes

1. 44AA Sister Size is 30F, 32E, 34DD, 36D, 38C, 40B and 42A.
2. 44A Sister Size is 30G, 32F, 34E, 36DD, 38D, 40C and 32B.
3. 44B Sister Size is 30H, 32G, 34F, 36E, 38DD, 40D and 42C.
4. 44C Sister Size is 30I, 32H, 34G, 36F, 38E, 40DD and 42D.
5. 44D Sister Size is 30J, 32I, 34H, 36G, 38F, 40E and 42DD.
6. 44DD Sister Size is 32J, 34I, 36H, 38G, 40F and 42E.
7. 44E Sister Size is 34J, 36I, 38H, 40G & 42F.
8. 44F Sister Size is 36J, 38I, 40H & 42G.
9. 44G Sister Size is 38J, 40I & 42H.
10. 44H Sister Size is 40J & 42I.
11. 44I Sister Size is 42J.

EU Bra Sister Sizes

65 Bust Bra Sizes

1. 65AA Sister Size is 65AA.
2. 65A Sister Size is 70AA.
3. 65B Sister Size is 70A and 75AA.
4. 65C Sister Size is 70B, 75A, and 80AA.
5. 65D Sister Size is 70C, 75B, 80A and 85AA.
6. 65E Sister Size is 70D, 75C, 80B, 85A and 90AA.
7. 65F Sister Size is 70E, 75D, 80CC, 85B, 90A and 95AA.
8. 65G Sister Size is 70F, 75E, 80D, 85C, 90B, 95A and 100AA.
9. 65H Sister Size is 70G, 75F, 80E, 85D, 90C, 95B and 100A.
10. 65I Sister Size is 70H, 75G, 80F, 85E, 90D, 95C and 100B.
11. 65J Sister Size is 70I, 75H, 80G, 85F, 90E, 95D and 100C.
12. 65K Sister Size is 70J, 75I, 80H, 85G, 90F, 95E and 100D.

70 Bust Bra Sizes

1. 70AA Sister Size is 65A.
2. 70A Sister Size is 65B and 75AA.
3. 70B Sister Size is 65C, 75A and 80AA.
4. 70C Sister Size is 65D, 75B, 80A and 85AA.
5. 70D Sister Size is 65E, 75C, 80B, 85A and 90AA.
6. 70E Sister Size is 65F, 75D, 80CC, 85B, 90A and 95AA.
7. 70F Sister Size is 65G, 75E, 80D, 85C, 90B, 95A and 100AA.
8. 70G Sister Size is 65H, 75F, 80E, 85D, 90C, 95B and 100A.
9. 70H Sister Size is 65I, 75G, 80F, 85E, 90D, 95C and 100B.
10. 70I Sister Size is 65J, 75H, 80G, 85F, 90E, 95D and 100C.
11. 70J Sister Size is 65K, 75I, 80H, 85G, 90F, 95E and 100D.
12. 70K Sister Size is 75J, 80I, 85H, 90G, 95F and 100E.

75 Bust Bra Sizes

1. 75AA Sister Size is 65B and 70A.
2. 75A Sister Size is 65C, 70B and 80AA.
3. 75B Sister Size is 65D, 70C, 80A and 85AA.
4. 75C Sister Size is 65E, 70D, 80B, 85A and 90AA.
5. 75D Sister Size is 65F, 70E, 80C, 85B, 90A and 95AA.
6. 75E Sister Size is 65G, 70F, 80D, 85C, 90B, 95A and 100AA.
7. 75F Sister Size is 65H, 70G, 80E, 85D, 90C, 95B and 100A.
8. 75G Sister Size is 65I, 70H, 80F, 85E, 90D, 95C and 100B.
9. 75H Sister Size is 65J, 70I, 80G, 85F, 90E, 95D and 100C.
10. 75I Sister Size is 65K, 70J, 80H, 85G, 90F, 95E and 100D.
11. 75J Sister Size is 70K, 80I, 85H, 90G, 95F and 100E.
12. 75K Sister Size is 80J, 85I, 90H, 95G and 100F.

80 Bust Bra Sizes

1. 80AA Sister Size is 65C, 70B and 75A.
2. 80A Sister Size is 65D, 70C, 75B and 85AA.
3. 80B Sister Size is 65E, 70D, 75C, 85A and 90AA.
4. 80C Sister Size is 65F, 70E, 75D, 85B, 90A and 95AA.
5. 80D Sister Size is 65G, 70F, 80D, 85C, 90B, 95A and 100AA.
6. 80E Sister Size is 65H, 70G, 75F, 85D, 90C, 95B and 100A.
7. 80F Sister Size is 65I, 70H, 75G, 85E, 90D, 95C and 100B.
8. 80G Sister Size is 65J, 70I, 75H, 85F, 90E, 95D and 100C.
9. 80H Sister Size is 65K, 70J, 75I, 85G, 90F, 95E and 100D.
10. 80I Sister Size is 70K, 75J, 85H, 90G, 95F and 100E.
11. 80J Sister Size is 75K, 85I, 90H, 95G and 100F.
12. 80K Sister Size is 85J, 90I, 95H and 100G.

85 Bust Bra Sizes

1. 85AA Sister Size is 65D, 70C, 75B and 80A.
2. 85A Sister Size is 65E, 70D, 75C, 80B and 90AA.
3. 85B Sister Size is 65F, 70E, 75D, 80C, 90A and 95AA.
4. 85C Sister Size is 65G, 70F, 80D, 80D, 90B, 95A and 100AA.
5. 85D Sister Size is 65H, 70G, 75F, 80E, 90C, 95B and 100A.
6. 85E Sister Size is 65I, 70H, 75G, 80F, 90D, 95C and 100B.
7. 85F Sister Size is 65J, 70I, 75H, 80G, 90E, 95D and 100C.
8. 85G Sister Size is 65K, 70J, 75I, 80H, 90F, 95E and 100D.
9. 85H Sister Size is 70K, 75J, 80I, 90G, 95F and 100E.
10. 85I Sister Size is 75K, 80J, 90H, 95G and 100F.
11. 85J Sister Size is 80K, 90I, 95H and 100G.
12. 85K Sister Size is 90J, 95I and 100H.

90 Bust Bra Sizes

1. 90AA Sister Size is 65E, 70D, 75C, 80B and 85A.
2. 90A Sister Size is 65F, 70E, 75D, 80C, 85B and 95AA.
3. 90B Sister Size is 65G, 70F, 80D, 80D, 85C, 95A and 100AA.
4. 90C Sister Size is 65H, 70G, 75F, 80E, 85D, 95B and 100A.
5. 90D Sister Size is 65I, 70H, 75G, 80F, 85E, 95C and 100B.
6. 90E Sister Size is 65J, 70I, 75H, 80G, 85F, 95D and 100C.
7. 90F Sister Size is 65K, 70J, 75I, 80H, 85G, 95E and 100D.
8. 90G Sister Size is 70K, 75J, 80I, 85H, 95F and 100E.
9. 90H Sister Size is 75K, 80J, 85H, 95G and 100F.
10. 90I Sister Size is 80K, 85J, 95H and 100G.
11. 90J Sister Size is 85K, 95I, and 100H.
12. 90K Sister Size is 95J and 100I.

95 Bust Bra Sizes

1. 95AA Sister Size is 65F, 70E, 75D, 80C, 85B and 90A.
2. 95A Sister Size is 65G, 70F, 80D, 80D, 85C, 90B and 100AA.
3. 95B Sister Size is 65H, 70G, 75F, 80E, 85D, 90C and 100A.
4. 95C Sister Size is 65I, 70H, 75G, 80F, 85E, 90D and 100B.
5. 95D Sister Size is 65J, 70I, 75H, 80G, 85F, 90E and 100C.
6. 95E Sister Size is 65K, 70J, 75I, 80H, 85G, 90F and 100D.
7. 95F Sister Size is 70K, 75J, 80I, 85H, 90G and 100E.
8. 95G Sister Size is 75K, 80J, 85H, 90H and 100F.
9. 95H Sister Size is 80K, 85J, 90I and 100G.
10. 95I Sister Size is 85K, 90J and 100H.
11. 95J Sister Size is 90K and 100I.
12. 95K Sister Size is 100J.

100 Bust Bra Sizes

1. 100AA Sister Size is 65G, 70F, 80D, 80D, 85C, 90B and 95A.
2. 100A Sister Size is 65H, 70G, 75F, 80E, 85D, 90C and 95B.
3. 100B Sister Size is 65I, 70H, 75G, 80F, 85E, 90D and 95C.
4. 100C Sister Size is 65J, 70I, 75H, 80G, 85F, 90E and 95D.
5. 100D Sister Size is 65K, 70J, 75I, 80H, 85G, 90F and 95E.
6. 100E Sister Size is 70K, 75J, 80I, 85H, 90G and 95F.
7. 100F Sister Size is 75K, 80J, 85H, 90H and 95G.
8. 100G Sister Size is 80K, 85J, 90I, and 95H.
9. 100H Sister Size is 85K, 90J, and 95I.
10. 100I Sister Size is 90K and 95J.
11. 100J Sister Size is 95K.
12. 100K Sister Size is 100K.