Bra Sizing Guide: Find Your Perfect Fit in Minutes

Have you ever put on a bra and thought, “This doesn’t feel right”? You're not alone. The truth is, most women are wearing the wrong size. That's not just uncomfortable—it's bad for posture, confidence, and your wallet. So let’s change that.

Whether you're shopping online at The Foundation or stepping into one of our welcoming boutiques, this bra sizing guide calculator is your starting point for comfort that actually fits. Let’s break it down step-by-step.

Why Bra Sizing Is Tricky (But Fixable)

Bra sizing isn’t universal. A size 12B in one brand might feel totally different in another. Why? Because materials stretch, styles vary, and our bodies change (thank you, hormones).

That’s why knowing how to measure bra size using a soft measuring tape is your secret weapon. Once you get the hang of it, you'll wonder why you ever relied on guesswork.

Step-by-Step: How to Measure Your Bra Size at Home

All you need is a soft measuring tape, a mirror, and about 5 minutes.

1. Measure Your Band Size

• Wear a non-padded bra

• Wrap the measuring tape snugly around your underbust area

• Ensure the tape is flat and level — not twisted

• Round to the nearest whole number

• If it's even, add 4. If odd, add 5

• That’s your band size

This is also referred to as your underbust measurement or band measurement.

2. Measure Your Bust Size

• Wrap the tape around the fullest part of your bust (overbust size)

• Keep the tape level but not tight — and definitely not loose

• Round to the nearest whole number

3. Calculate Your Cup Size

• Subtract your band size from your bust size

• Each inch difference equals a cup (1" = A, 2" = B, etc.) — this is a general guideline and aligns with most Australian bra sizing systems, though individual brands may vary slightly.

Example: Bust 37" - Band 34" = 3" difference = C cup

✅ Result: 34C (your ideal bra size)

This method is perfect for finding your correct size. If your current bra size doesn’t match this, you might be wearing the wrong size.

How to Calculate Your Bra Size

While we don’t currently offer an interactive bra size calculator, this guide gives you all the steps you need to accurately measure your size at home. Until we release a tool in the future, this manual method is your go-to.

Lingerie Sizing Chart: Quick Reference

Here’s a quick look at typical measurements and corresponding cup sizes:

Check out the complete official size chart for more variations, including Australian size references.

You can also browse curated products by size using our Shop by Size page.

Bra Fit Tips You’ll Wish You Knew Sooner

• Always scoop and swoop your breast tissue into the cups

• Tighten the shoulder straps only until they comfortably support

• If your band rides up, try a smaller bra band size (this refers to your underbust measurement)

• If cups gape or overflow, you may need a different cup size

• Try your sister size (e.g. 12C = 10D or 14B) if your fit is almost right

These bra fit tips can make your daily wear more comfortable and flattering.

Why Fit Matters (More Than You Think)

Wearing the right bra size isn’t just about comfort. It affects:

• Posture: No more slouching

• Confidence: You’ll feel the difference (and others will notice)

• Longevity: A proper fit protects the bra’s shape and function

If you’ve ever struggled with uncomfortable straps or shifting cups, chances are you’re in the wrong bra size.

Let The Foundation Help You Find Your Fit

Want expert help? Book a free fitting at one of our welcoming boutiques. From frame size to natural size fluctuations, our trained staff consider it all.

Find your nearest location: In-Store Fittings at The Foundation

Can’t make it in-store? Our team is happy to guide you online or by phone using accurate bra size methods.

Explore bestsellers like:

• Chantelle SoftStretch Full Briefs

• Chantelle Smooth Comfort Hi Waist Briefs

Conclusion: Your Best Bra Fit Is Just a Measurement Away

Don’t settle for discomfort. With the right measurements and tools, your perfect bra fit is just a few quick steps away. From the correct underbust size to finding your alternate size, this guide has your back — literally.

Bookmark our guide, refer to the lingerie sizing chart, and explore more sizes on our Shop by Size page.

FAQs

1. How often should I measure my bra size or be fitted for a new bra?
Every 6–12 months or after significant weight changes, pregnancy, or surgery.

2. What if I’m between cup sizes?
Try a sister size — for example, 14C = 12D or 16B.

3. Do different brands have different sizing?
Yes. That’s why we recommend visiting us for a bra fitting as we can help you navigate the differences between the brands. Measuring with a soft measuring tape will simply give you a vague idea of your approximate size but each brand is different. 

4. Can I use this method for T-shirt bras or sports bras?
Absolutely. This technique helps with all types of bras, including T-shirt bras.

5. What’s the most common bra mistake?
Not visiting an expert for a personalised bra fitting! Some bras fit tight in the under bust and others may have a deeper (bigger) cup. It is common to wear a different size bra across different brands. The most common bra mistake we see is a cup that is too small and cutting into the breast tissue. Visit us for a fitting or recalculate your underbust measurement and bust size for the most accurate bra size.

Need help? Visit our Shop by Size or book an In-Store Fitting. We’re here to help you find your true bra size.