Updated on July 7th, 2023 at 06:40 pm

Finding the right bra size isn’t as simple as you think. Bra sizes might vary throughout life due to pregnancy, fluctuating weight, and age. Unfortunately, we aren’t taught how to measure bra size in school or by our parents.

Most women choose bras by their look and feel while holding them against their boobs before a mirror. While this trick works for workout shorts, gym leggings, and other clothing, it doesn’t work for bras.

Statistics show that 80% of women wear the wrong bra size, indicating that women need help determining their bra sizes. With the internet full of conflicting information on bra sizes, I’ve taken it upon myself to share accurate information and ensure women get the right bra size and superior comfort and support.

Why is it crucial to have a well-fitted bra?

image of elomi women's cate full cup bra - Extra Large Living

Aside from comfort, wearing a well-fitted bra maintains good health. Wearing the wrong bra often contributes to shoulder, back, and neck pain, poor posture, and saggy boobs. Breasts have a 4cm range of sway in each direction. Therefore, something as gentle as walking up a flight of stairs without a bra is enough to stretch the delicate skin around the breasts.

It’s scary, but luckily, you’re about to learn how to measure your bra size accurately.

How often should you measure your bra?

There isn’t an exact date for this, but many lingerie brands recommend measuring your bra size every six months or when you go bra shopping. These regular measurements are crucial since bra sizes change often due to weight and hormonal changes.

While you’ll learn how to measure bra size independently, it’s advisable to use a professional. A professional will guide you on the right size and the bra style that suits your figure and shape.

For instance, triangle bras aren’t ideal for women with larger boobs, but they are perfect for smaller-breasted women. On the other hand, plunge bras provide women with big boobs with the support and lift they need.

Why do bra sizes change?

Several factors affect bra sizes:

Weight gain or loss

Losing or gaining several pounds impacts bra size since breasts are mostly fat tissue. So when you notice some weight loss, you should take new bra size measurements.

According to experts, losing 20% of your body weight means dropping one cup size. Generally, a woman weighing 200 pounds needs to lose 40 pounds to drop a cup size.

Hormone fluctuations during your period

Your menstrual cycle causes significant boob size, shape, and texture changes. In the first half of the cycle, the body produces estrogen, which triggers ovulation and stimulates milk ducts in breast tissue. In the second half of the menstrual cycle, the body produces progesterone, which triggers the formation of milk glands, resulting in some soreness and swelling. These changes result in bigger and lumpier breasts than usual.

While we aren’t suggesting you measure your bra size every month, it helps to have specific bras for your time of the month when your boobs are a little fuller.


Boobs look different during the teen years and when approaching menopause, mainly due to hormonal changes. Production of estrogen reduces, causing connective tissues in your boobs to lose elasticity and become dehydrated. Moreover, since the breast tissues stop preparing for milk production, they shrink, causing them to become less perky and reduce in size.


When you start working out and lifting weights, you’ll notice your boobs will get perkier. Pectoral exercises strengthen pectoral muscles sitting behind the breast tissue. So, if these muscles bulk up slightly, they’ll push out your breasts outside a little more.

Note: while chest exercises don’t increase breast size, they grow the pectoral muscles and create the appearance of bigger boobs.

Birth control

Hormonal birth controls like hormonal IUD, the shot and pill, do a lot more than regulating your period and preventing unintended pregnancies. They can also affect breast size by causing water retention when you first start using birth control.

How to measure bra size

A lot goes into measuring bra size than simply using a measuring tape to mark band size. In addition to band size, you need to measure bust and cup size and I’ve outlined how to do it right in three steps. But before you dive in, ensure you are wearing a simple non-padded bra that holds your boobs in the right position. Also, arm yourself with a soft tape measure.

Step 1: Measure band size

  • Place your measuring tape snugly around the ribcage, right underneath your bra’s band.
  • Ensure that it’s parallel to the ground.
  • Note the measurements in inches.
  • If it’s an even number, that’s your band size. But if it’s an odd number, round it down or up to the nearest even number. Always round down if you are a little soft around the band. But if you are leaner and don’t have ample give around the band, round the measurement up.

Step 2: Bust measurements

  • Place the measuring tape around your back and at the bra band’s level
  • Measure across the fullest part of your bust, making sure the measuring tape is snug against your breasts and parallel to the floor
  • Take several deep breaths and let the tape rest in the most comfortable position
  • If the number is over half an inch, round it up to get your bust size

Step 3: Determine cup size

Now, this is where things get a little tricky since sup sizes vary between brands. However, the most common method of determining cup size is subtracting band size from bust size and matching the difference to the appropriate cup size on a bra size chart.

Bust measurement – Band Measurement = Cup Size

  • 1″ – A cup
  • 2″ – B cup
  • 3″ – C cup
  • 4″ – D cup
  • 5″ – DD cup
  • 6″ – DDD cup

After determining your band size and cup size, pair the two to determine bra size. Let’s take it from the top for a better understanding. Say your bust size comes to 36 inches and your band size is 34 inches; the difference is 2 inches. From a bra size chart, 2 represents a B cup which means your bra size is 34B.

When measuring bra sizes, always remember bras aren’t universally designed and constructed. You might be a size 34B in one brand but a different size in another brand/ store or country.

Here’s a quick cup size conversion chart to guide your choice.

image of international breast sizing conversion chart - Extra Large Living

How to check if your bra fits properly

Aside from this, here are several checks to use to determine if you have the correct bra size.

The bra shouldn’t leave dents on the skin

If you wear a bra that’s too tight, you’ll have indentations in the skin. This is a sign that you need to adjust the clasp, straps or get a bra that’s a size up. But if you are already on the largest-sized clasp and still getting dents, you should get a size up.

Bra cup fit

Whether you love lace cups or mesh cups, the following rules apply.

If the bra cups are overflowing or gaping, you are wearing the wrong bra. The cup should comfortably hold your boobs without creating a double boob, which means the cup size is very tight or gaping, which means the bra is too big.

A good check for a well-fitting cup is that the underwire on the side sits on the rib cage and not on breast tissue.

Bra band fit

The under band of a bra can be painful if it’s not the right fit. Since bra support is from the band, it must be the perfect fit.

A well-fitting bra band should be parallel to the front of the bra. Also, the under band should pull away slightly from the body when you pull without much resistance. A golden rule of thumb is to allow a 1cm pull from the side and 2 inches from the back. If it digs into the skin, the size is too small. Also, the bra is big if the band rises from front to back, or boobs are peaking at the bottom.

If you determine the cup size or band is wrong, you should measure the size again instead of going a size up or down. If you change one of the sizes, you should adjust the other.

Bra strap fitting

If your bra has slipping straps, leaves marks, or digs into your skin, you either have the wrong bra style for your breasts or an ill-fitting bra.

If the straps are too tight, it’s a sign the band isn’t providing the support it should. If the straps keep falling, you should readjust them. If they still don’t sit right, you should recheck the size and pick a better bra style.

A plunge bra and t-shirt bra are ideal for different boob shapes. A great way of checking if the straps fit correctly is to try and fit two fingers under straps and pull upwards from the shoulder.

Center front sit

The center front is that section between the cups. The wire on the center front should sit flat against your body. If it’s gaping, the cup size is small, and if it’s digging into your sternum, then the band size might be too small.

Bra sister sizes

A sister size is a size that will provide you with the same cup size but a larger or smaller band size depending on your needs.

image of table comparing bra sister sizes - Extra Large Living

If the band in your usual size feels a little loose, try a size to the left of your current size. And if it feels like the bra is too tight, choose a size to the left of the current size. Also, you might want these alternate sizes when the style you want isn’t available in the size you need.

Taking measurements of sports bra

Finding a well-fitting sports bra is as important as finding a regular bra. The sports bra should offer comfortable support for your boobs through rough workout sessions and is more important when you have big boobs.

According to a study by the University of Portsmouth, breasts can move by 14 cm during strenuous and vigorous exercises. If you put them under this stress often, you risk causing permanent damage to Cooper’s ligaments that hold the breasts firm.

Unlike a regular bra, where your choice is between wireless, wired, or strapless styles, sports bras are available in different support options.

  • Low support – ideal for walking and yoga and perfect for small cup sizes between AA and B.
  • Medium support – ideal for strength training, cycling, dancing, skiing, and low impact exercises.
  • High support – ideal for HIIT, aerobics, and running. They are also perfect for large cup sizes D and over.

How should a sports bra fit?

Overall, a sports bra should be snug but not very tight. A sports bra that’s perfect for you doesn’t mark the skin, restrict breathing, or cut off circulation. Try jumping with the sports bra on to ensure it’s comfortable, stays in place, and doesn’t restrict movement.

Once you find one that fits great, remember what size it is for future reference. However, bear in mind you’ll need to replace the sports bra after 30 or 40 washes since they lose their elasticity fast.

Are sports bra sizes the same as normal bra sizes?

Yes, they are. But it’s not always straightforward. The sizing method depends on the bra’s level of support and brand. Some bras that provide a lot of support are sized according to band and cup size like regular bras or plus-size bras. However, other brands and sports bras that provide medium to low support use XS to XL+ scale. You need to convert bra size to its corresponding size in the XS – XL+ metric sizing for these options.

Choosing the right bra size is crucial for your health. But aside from bra size, support and comfort, you should choose the best size based on design and bra styles.

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