How to Measure for a Maternity Bra? Follow These Guide

Published by 
Jess Miller
Last updated: 
March 31, 2023

Maternity clothes are mystifying--when should you use them? Are they a waste of money or a godsend? Maternity bras are even more complicated, but I’m pregnant, and I wanted to learn how to measure for a maternity bra so I could find some that are more comfortable than my normal bras. Here’s what I found out!

To learn how to measure for a maternity bra, wear a bra that’s not padded or compressive and use a tape measure to measure under your breasts at the ribcage and then across your breasts at the fullest point. The difference is your cup size, and the band size is the measurement you took at the ribcage.

Still confused? I’ll break it down a little more.

Measuring Yourself vs. a Professional Fitting vs. Using a Maternity Bra Calculator

There are roughly three different ways to figure out your bra size:

  • Go to a lingerie store for a professional bra fitting (this is our favorite option)
  • Use a measuring tape and do the calculations yourself
  • Measure yourself and use a maternity bra calculator online

All options get the job done, but if you’ve never been fitted before or suspect you’ve been making do with poorly-fitted bras, it’s worth it to go to a high-quality store to get a professional fitting. If possible, visit a store that specializes in maternity clothing or undergarments, as the fitters there will be experts on how breasts change and evolve during pregnancy and after and can give you a better idea of what to expect.

Plus, every woman is different--two women who are both a 36C, for example, can still have completely different needs and wants when it comes to bras. Good fitters know their inventory well and can steer you towards what makes sense for your body and preferences and can also help you make sure you’re getting a good fit, regardless of what the size label says.

How to Measure Your Bra Size

Not all people have access to professional fittings, however--which is why I’m writing this article! When it comes to measuring yourself, here’s a more detailed explanation:


Wear an Unpadded Bra

Do wear a bra when you measure yourself, but make sure it’s not padded and make sure it’s not compressive, like a sports bra.


Use a Tape Measure

Using a tape measure, take two measurements. The first is horizontally right underneath your bust, at the rib cage. This is your band size. The second measurement should be around the fullest part of your breast, horizontally and usually right at the nipple line.


For both measurements, hold the measuring tape firmly but not tightly. The difference between the larger measurement and the band size is your cup size. For example:


  • A 1” difference is an A cup
  • A 2” difference is a B cup
  • A 3” difference is a C cup
  • A 4” difference is a D cup
  • And so forth!  

As you can probably imagine, there’s quite a bit of variation when it comes to cup sizes. That’s why it’s so important to focus on the quality of the bra, itself, as well as how it fits you, regardless of what size it says it is. Just like with other types of clothes, bra sizes can run big or small.

If you’d rather not do the mental math, you can use a maternity bra calculator like the one here.

How Do I Know If My Maternity Bra Fits Correctly?

Pregnant women is wearing a maternity bra while standing outside her house

Image by Frederico Freddy from Pixabay

Here’s how bra experts make sure a bra fits correctly:

  • Try your bra on under clothes, and make sure you look at the fit when you’re standing up and sitting down, as well.
  • The band should sit snugly against your skin, with just enough room for you to slide two fingers underneath comfortable. It should also sit horizontally underneath your bust--your straps should be pulling it up towards your shoulder blades.
  • The straps shouldn’t dig in or pinch, and you should be able to slide two fingers comfortably underneath them, as well.
  • The cups should also fit comfortably--they shouldn’t overflow, pull away from your ribcage, or gap heavily. The center part in between the cups should lay flat against your chest.

Your maternity bra should also be comfortable and suited to your life. Many women, for example, opt to skip underwire as it tends to dig in. Instead, they opt for supportive mesh or foam frames or molded cups.

You should also consider the softness of the material. It’s common to become extremely sensitive and irritated by fabrics that you once thought were cute or pretty--things like lace, for example.

When Should I Start Wearing a Maternity Bra?

Here’s the truth about how to measure for a maternity bra: you don’t technically need a maternity bra. That’s right! One of the things I discovered in my research is that there’s no such thing as a maternity bra. Instead, nursing bras are used during pregnancy or marketers use the maternity label to specify that the bra is suitable for use during pregnancy.

That said, your breasts will likely change significantly during pregnancy. They’ll grow heavier and can become excruciatingly tender, and you can even find yourself leaking by the end of your pregnancy and in need of a bra that will accommodate pads.

Plus, you might find yourself reaching for a bra more and more often, even if you used to let the girls go free, as you now crave the extra support. Whatever the case, most experts recommend going in for a bra fitting at the beginning of your second and third trimesters or about every six to eight weeks.

Truly, however, you should get fitted any time your current bra starts getting uncomfortable.

What’s the Difference Between a Maternity Bra and a Nursing Bra?

If you start looking for a maternity bra, you’ll likely be confused by how often you get handed nursing bras. “I’m not nursing yet,” you might think or, “I don’t plan on nursing at all.” The truth is, as I’ve mentioned, there’s no such thing as a maternity bra.

However, most of the things a pregnant woman needs in a bra are also the things a nursing mom needs in a bra, which is why the two terms are often used interchangeably. Plus, many women find that using nursing bras while they’re pregnant means they have bras to use when they’re nursing, as well, helping those dollars to stretch a little further.

The only thing that a nursing bra has, technically, that other bras don’t have is a clip down front that allows you the nurse easily. These clips might seem weird if you’re not used to them, but they won’t get in your way if you’re not nursing, and many women find that nursing bras are so stinking supportive and comfortable that they wear them even when they’re not pregnant or nursing.

What to Look for in a Maternity Bra

I’ve learned the hard way that just because a bra has the maternity label doesn’t mean that it works well for pregnant women. Some less-than-helpful bra makers simply use the label as an excuse to charge extra.

So, it’s ultra important to take matters into your hand and carefully evaluate the bras you’re interested in. Here’s what to look for:

  • Breathable, stretchy fabrics are a must-have both for comfort and to accommodate your growing breasts. This helps bras last longer for you. Keep in mind that there’s a difference between something like a sports bra, that compresses, and a nursing bra, that’s designed to be supportive while accommodating size increases and decreases.
  • Cotton is always a good choice, but more and more we’re finding the best bra makers relying on blends that are exceptionally strong while also being breathable and soft. Look for manufacturers that have high manufacturing standards, so you avoid fabrics with toxic chemicals.  
  • Racerbacks and t-backs tend to offer additional support because they spread the weight across your back and shoulders. Also, make sure the straps are nice and wide--skinny straps can be downright miserable.
  • You can find maternity and nursing bras with underwire, but don’t be afraid to try them without underwire. Again, bra technology has improved significantly in the last decade.
  • It’s also important to utilize specialty bras, like sports bras (here’s one of my favorite maternity/nursing sports bras) and sleeping bras. Sleeping bras are usually extremely soft and offer just enough support to make sleeping more comfortable, especially when you’re on your side, while good maternity or nursing sports bras will help you keep up with an active lifestyle for as long as possible.

Whatever bra or bras you end up choosing, the important thing is that you’re comfortable. Don’t worry about the rules, but do worry about finding a fit and fabrics that feel great for your entire months.

Featured Image by Fernando Zamora from Pixabay

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