How to Find the Right Bra Size


It may seem like the task of finding the correct size bra boils down to a little math. If only it were this simple!

While finding the correct size is a matter of measurement, finding the best fit for you really takes a little more trial and error.

The truth is, you know your body, style and comfort needs better than anybody else. So while measuring (or preferably being measured) is important, a fitting is really a dialogue between you and your bra-fitter. 

In order to have a good dialogue, you’ll need to know a little bit about how bras are measured, how they’re supposed to fit (especially if they're a wireless bra) and what you need to bring to the conversation.

1. Know the Signs of a Wrong-Sized or Ill-Fitting Bra

Many women hold tight to the idea that they’re one size or another. We might even have ideas that there’s an “ideal” size we want to be.

But once you put on any item of clothing, the numbers on the label don’t matter as much as the fit, your comfort and confidence. So, if you’re hanging on tight to an idea around size, let it go for a moment. Instead, reflect on how your bra actually feels to wear. 

There are some tell-tale signs you’re wearing the wrong size bra and you should be alert to them! You do not have to put up with these. Wearing a bra should not involve:

  • Your straps slide off your shoulders, even after you’ve tightened them
  • You shift around in your cups
  • Your breasts bulge out of your cup or sides
  • The band rides up your back
  • The underwire hurts your ribcage
  • Your bra leaves painful marks on your skin
  • You’re plain uncomfortable

2. Understand the Ways (Yes, Plural) Bras Are Measured

Many websites and online bra calculators take one (simple) way of measuring a bra and instill an idea that you can do this yourself and the measurement will universally apply across all brand manufacturers!

Sounds too good to be true? Well, sometimes. 

Now, don’t get us wrong: It can be a very worthwhile exercise to take the time to measure yourself and understand how bra sizing is calculated. You'll need to take two measurements: Your band and the fullest part of your breasts.

You can learn more about how to find your bra size with a measuring tape over here.

But bra size is more complicated and less universally consistent than many websites would lead you to believe. In fact, there are nuances like whether to add inches to the band size that can be hotly debated across brands. 

There’s also the concept of “sister sizing” that can come into play when you’re shopping across brands. Knowing your “sister size” is useful to accommodate for size differences between brands. 

Sister sizing works as follows: If you go up in the band size, go down in the cup size and vice versa. For example, a 36C could possibly fit a 34D or a 38B. If you’re a 32C, for some brands you might find bras that fit better in a 34B or a 30D

3. When in Doubt, Round Up

Very few of us hit even numbers perfectly, either with our band size or our bust size (cup size) measurement. Plus you may observe that one breast is larger than the other and wonder about cup size. (By the way, asymmetry is completely normal, by the way, our bodies as a whole are not perfectly symmetrical. Your facial features, shoe size etc. are rarely a perfect mirror image of the other side!)

When it comes to taking a bra measurement, odd and non-whole numbers on the measuring tape can cause confusion. The rule of thumb is to always round up. Bras should be snug fitting and so if you round down, you risk wearing a bra that’s way too tight and uncomfortable. You can also try on the “sister sizes” to see if giving or taking from band and cup sizes makes a better fit for you.

Again, not to bang the drum, it’s these little complexities that make it ideal that you get help to find a bra size, which leads to the next point...

4. Go for a (in Person or Virtual) Fitting 

It’s really important to understand the complexities of bra-sizing and fit when shopping so that you can get the comfort you deserve, and avoid costly mistakes. 

The wrong size or fit of bra will ruin your day. You’ll feel uncomfortable, maybe even sore, and just want to get home so you can rip the damn thing off. That’s why it’s generally recommended you go for a professional fitting rather than relying on your own, at home measurements.

Luckily, there are virtual options too, letting you have the best of both worlds: The comfort of your own home and reassurance of an expert.

At Knix, we know it can be especially daunting to make a bra purchase online. That’s why we developed our virtual fit program. Learn more about it today and book your appointment!

What to Expect from a Knix Virtual Fitting:

  • Book your virtual fitting here
  • We’ll connect you with one of our expert Knix team members for a 1-on-1 fitting session over video chat. 
  • For your bra fitting, we recommend you wear a bra with little or no padding and a fitted t-shirt to make sure we get an accurate measurement. You’ll also need either a) a soft measuring tape or b) a piece of string or cord and a tape measure or ruler.
  • With different styles and sizes for 30A to 42G in the world’s most comfortable and supportive wireless bras, our fit experts can help you get into something that you will love to wear every single day.

5. Make Sure the Band is Snug (Not Loose, or Tight)

You should get most of your support from your band, not your shoulder straps. If too much of your support is coming from your shoulder straps, it can cause those straps to really dig into your skin, causing red, indented marks. Over time, it can also cause shoulder strain.

In order for your band to give you more support so your shoulders get some relief, it’s important that your band size fits snugly. Too loose and you risk it not doing its job effectively. Too tight and you’re back to the problem of pain/discomfort.

One analogy that may be a useful analogy is for your band to fit like a seat-belt. It’s definitely going to make you feel “held in” without causing pain, discomfort or restricting certain movements.

It’s important to note that with many bras, there’ll be a bit of a “breaking in” period. This means the band size may feel a little more restrictive on the first try than it does once you’ve worn and washed it once or twice.

6. Learn About Breast Shape

Even if you measure a consistent bra size across every brand, it wouldn’t mean that every bra is right for you. That’s because apart from bust size, we’re all shaped differently .

After years of reading women’s magazines and hearing women’s bodies described, we’re all generally very aware of our body shape. But we often aren’t as aware of our breast shape, and what breast shape means when we’re looking for the correct fit bra. 

Let’s look at some of the different breast shapes (regardless or bust size):

  • Full, round breasts
  • Compact, high or athletic breasts
  • Bell or teardrop shaped breasts
  • Wide set or “east west” breasts
  • Asymmetric breasts

Also, it’s important to note that you might not sit neatly in one of these shape categories. As with body shape, we’re all different. This is exactly why it can be so challenging to find the correct fit — and why you might need some help!

7. Determine the Best Style for Your Size, Shape and Occasion

While all your bras should offer good fit, support and comfort, there are many styles of bras designed for different clothes, activities and occasions.

A bra that fits you well for everyday wear may not be the right bra for playing sports in, for example. 

So, while it’s absolutely important to focus on finding the correctt size bra, it’s also important to think about the design for your lifestyle and when you’ll wear it. It won’t feel like the right size if it doesn’t also consider these factors.

8. Nothing Stays the Same: Your Breasts & Body Change

We all know our bodies change over time. We might lose or gain weight, add or lose muscle without changing weight, or go through major bodily events like surgery, puberty, pregnancy, breast-feeding, menopause, aging etc. that impact our bodies, including our breast shape.

But even much more subtle and normal fluctuations can impact the size of breasts. Within our menstrual cycle alone our breasts might change size, become tender and even painful. This can mean that the bras that feel comfortable during one stage of your menstrual cycle might be dramatically uncomfortable when you’re premenstrual, as an example.

This is why finding the right size bra is not a “one and done” event. In fact, it’s really worth getting fitted for a bra annually. 

You Don’t Have to Go it Alone

There’s a lot to consider when finding the right bra size, style and design. That’s why it’s so strongly recommended you go for professional fitting (either virtual or in store). 

The right size bra can make a huge difference to your comfort, confidence and even how your clothes fit. There’s really no reason for you to tolerate an ill-fitting, uncomfortable bra. We’re here to help!