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How to Measure Your Bra Size for Maternity & Nursing Bras

They’re changing every day, they’re sore, and your partner seems to find them irresistible. What’s going on? How to measure your bra size? Here’s our quick easy guide to fitting a bra properly!

Bra Sizes & Why They Change

Bra sizes for maternity and nursing bras are the same are those for normal bras (you’ll find a full description of the complicated way bra sizes are determined later in the article), but you’ll find that maternity and nursing bras are often multi-sized e.g 34 B/C or Medium, which tends to make it easier. Either way it’s important to be sure that you know about they way your shape changes so you can measure your bra size and get the best bra for you:

Your breasts are made up of fatty tissue, connective tissues and glands, enclosed in skin. During your pregnancy, the mammary glands expand and fluid is stored in the tissue.

Each breast will become 300-500g heavier (it’s like having a pair of chicken breasts tucked in each bra cup!). As you can imagine, this puts the surrounding skin and tissue under a lot of strain. Your rib cage will expand slightly and your bra size may increase by 1-2 sizes – 34B to 38D isn’t unusual. While your partner may appreciate this, it isn’t without its problems.

A couple of days after your baby is born, you will notice your cup size grow again – that’s your milk arriving. This is often associated with tenderness or soreness. But while your cup size is growing,  the measurement around your rib cage will slowly return to normal.

 What do I need to do?

If your breasts aren’t adequately supported during pregnancy, they can loose their perky shape. They may also cause tension in your neck and back, but there’s a solution to this: find a good set of maternity bras. After baby is born, you’ll need to handle your breasts with utmost care to avoid mastitis. A good nursing bra will support them during this period. But first you’ll need to know how to measure your bra size….

How to Measure Your Bra Size

Quick Method of Bra Sizing

Band Size – Measure around your ribcage in inches, then add 4 (called the Underbust +4 method) to get this

Cup Size – Measure around the fullest part of the bust (over the nipples) – take away ribcage measurement. A difference of 6″ is a B cup, 7″ is a C cup, 8″ is a D cup, 9″ is a DD cup and so on.

Widely different bras can have the same cup volume. We all know by common sense that someone boasting of a 36DD is going to have more breast volume than someone who has a 30DD, but why are the both called DD then? It’s because the cup letter only lets you know the difference between the underbust measurement and the full bust measurement. The result of this is that you get sister sizes – different band meaasurements but exactly the same cup volume…….

So these all have the same cup volume:     30F, 32E, 34DD, 36D, 38C, 40B
And so do these :                                                  30D, 32C, 34B, 36A.

Imagine being a 36A all your life and not knowing you breasts are actually the same size as a 30D !!!

And that’s where adjusting band sizes and cup together can get you a better bra sizes, because while cup volume isn’t adjustable on most bras, nearly all bra have band adjustments.

So if we’re considering the problem above where someone trying a 34D has a band that’s slightly loose but fine on the cup and they want to get a better fit, they should first try a 32E, because by going down a band size you need to increase the cup size to ensure the cup volume stays the same……

What about if the band is too tight but the cup is OK? Well use the same rule of thumb and when you go up a band size, decrease the cup size to compensate. And if the band is OK and the cup doesn’t fit, just keep the band size steady and go up one cup at a time until your breast is fully enclosed by the cup, it doesn’t ride up and it doesn’t double boob.


 How to Measure Your Bra Size by Using a Chart

1.Stand with a mirror behind you. Take the tape measure and wrap it around you under your bust. Look over your shoulder in the mirror to ensure the tape is lying flat and not sliding down your back. Take a firm measurement. This will tell you your bra size.

2.Repeat this step, this time measuring across the top of your bust (over the broadest part and across your nipples), again checking the tape measure isn’t sliding down at the back. Take a measurement. This will tell you your cup size.

Under Bust Across Bust Bra Size









27-28 70 33-34 85 32 70 85 B
34-35 88 C
35-36 90 D
36-37 93 DD
37-38 95 E
38-39 98 F
39-40 100 G
40-41 103 H
41-42 105 J
42-43 108 K
Under Bust Across Bust Bra Size
29-30 75 35-36 90 34 75 90 B
36-37 93 C
37-38 95 D
38-39 98 DD
39-40 100 E
40-41 103 F
41-42 105 G
42-43 108 H
43-44 110 J
44-45 113 K
Under Bust Across Bust Bra Size
31-32 80 37-38 95 36 80 95 B
38-39 98 C
39-40 100 D
40-41 103 DD
41-42 105 E
42-43 108 F
43-44 110 G
44-45 113 H
45-46 115 J
46-47 118 K
Under Bust Across Bust Bra Size
33-34 85 39-40 100 38 85 100 B
40-41 103 C
41-42 105 D
42-43 108 DD
43-44 110 E
44-45 113 F
45-46 115 G
46-47 118 H
47-48 120 J
48-49 123 K
Under Bust Across Bust Bra Size
35-36 90 41-42 105 40 90 105 B
42-43 108 C
43-44 110 D
44-45 113 DD
45-46 115 E
46-47 118 F
47-48 120 G
48-49 123 H
49-50 125 J
50-51 128 K


What sort of maternity bra should I buy?

A soft bra is usually best, as underwired bras can cause restriction and cut in as you grow. There are design features in maternity bras that help keep your breasts in good shape:

– Soft breathable materials that expand with you and don’t cut into the skin.

– An integrated support system

– Wider straps to ease the strain on shoulders and neck

If you’re used to underwired bras, you’ll be pleased to hear that there are underwired bras designed for wear during pregnancy and breastfeeding – they’re designed specially for your changing shape, with soft wires. Don’t forget that these are not interchangeable with normal underwired bras.

Most bras are now designed with nursing clips, so that you can use them after the baby is born too; but because your breasts continue to change shape, you’ll probably find you need at least one new bra (see nursing bras).


What sort of nursing bra should I buy?

After the baby is born, you will notice your bra fastenings getting looser as your ribcage shrinks, but your breasts will almost certainly be spilling over the cups.

You might be able to continue with your maternity bras if they have nursing clips, but you will probably need a larger nursing bra to see you through the first 5-6 weeks of nursing.

Customers usually become big fans of the Bravado bra – even if the soft style initially put them off. Women often come back and buy two or three more to keep them going. The moral of the tale? Try a soft bra, and see what a difference it makes.


 Maternity Bra Fitting Checklist

When you receive or choose your new bra, check that you can tick all of the following:

– Does it fasten comfortably on the tightest fitting hooks?

– Does it have at least ½-1 cup’s worth of growing room (there’s a handy way to check this: pop your hand half way in the cup: does it still stretch to fit?)??

– Does it feel comfortable and give medium support??

– Does it stay where it is when you lift your arms??

– Does the underbust band stay firmly beneath your breast??

– Does it give your bust a natural shape??


Nursing Bra Fitting Checklist?

You can try on nursing bras from about 37 weeks. Check that you can answer yes to all of the following:?

– Does it fit comfortably on the loosest hooks (widest setting)??

– Does it have at least ½-1 cup’s worth of growing room (pop your hand half way in the cup: does it still stretch to fit?)??

– Does it feel comfortable and give soft gentle support??

– Does it stay put when you lift your arms??

– Does the underbust band stay firmly beneath your breast??


If you need any more info, please contact me using our Google Groups Q&A  

I hope this has helped you understand bra sizes and explained how to measure your bra size correctly.