The Bra Fitting Guide
Everything you need to know about measuring your bra size at home, understanding sizing, and getting the right fit.
If you find yourself tugging, adjusting, or constantly fidgeting with your bra throughout the day, chances are it’s not quite doing its job. A good bra should sit there quietly, giving you support without digging in, slipping down, or making you think twice about it. Yet so many of us are wearing the wrong size, often without even realising it. Bodies change, bras stretch, and UK sizing often leaves you second-guessing.. That’s where this guide comes in. We’re here to make bra fitting simple and even a little fun. From measuring yourself at home, to understanding how cup sizes and bands really work, to spotting those small fit quirks that make a world of difference, consider this your go-to guide for bras that actually feel like they were made for you.
Words: Melisa Rustemova - Published: 05.10.25
How to Measure Your Bra Size at Home
If you’ve ever stood in a fitting room wondering, 'How do I figure out my bra size?' You’re definitely not alone. The good news is that measuring your bra size at home is quick, easy, and surprisingly helpful. It’s also the simplest way to understand how to calculate bra cup size in the UK without the guesswork.
What You’ll Need
All you need is a soft tape measure, a mirror, and a non-padded bra - or no bra at all. Heavily padded styles can throw measurements off, so it’s best to keep things simple. Stand naturally, breathe normally, and try not to overthink it.
Step 1 – Measure Your Band Size
Wrap the tape measure around your ribcage, sitting directly under your bust. It should feel snug but not uncomfortable, sitting straight all the way around. This number matters more than you might think, as the band does most of the heavy lifting when it comes to support. In UK sizing, round to the nearest whole number to get your band size.
Step 2 – Measure Your Bust Size
Next, measure around the fullest part of your bust. Keep the tape level and relaxed, using a mirror to check the back if needed. The tape should rest lightly against your body, without digging in or slipping down. Standing naturally, rather than puffing your chest out, will give you the most accurate result.
Step 3 – Calculate Your Cup Size (UK Guide)
To work out your cup size, subtract your band measurement from your bust measurement. The difference between the two is what determines your cup size in UK sizing. Each inch equals a cup size, starting from an A. It sounds technical, but once you’ve done it once, it quickly makes sense and gives you a great starting point.
Understanding UK Bra Sizes
UK bra sizing can feel a bit misleading at first glance. The number and letter look straightforward, but they are designed to work together, not independently. Small changes in either can affect how a bra fits, which is why your size might shift over time or feel different between styles. Things like body changes, fabric stretch, and brand design all play a part, so it’s normal for your fit to need a refresh now and then rather than staying the same forever.
How Bra Sizes Actually Work
A bra size is made up of a band number and a cup letter, but the cup letter on its own doesn’t tell the full story. Cup sizes change depending on the band, which means they’re relative rather than fixed. This is why two bras with the same cup letter can look and feel completely different.
Is a 36C Bigger Than a 34C?
This is one of the most common fitting questions, and the answer is yes. A 36C is bigger than a 34C because the cup volume increases with the band size. Once you know this, it becomes much easier to understand why changing band sizes often means changing cup sizes too.
What Are Sister Sizes?
Sister sizes are bras with the same cup volume but different band sizes. For example, a 34D, a 36C, and a 32DD all hold a similar amount of breast tissue. Sister sizing is handy if your usual band feels too tight or too loose, but the cups fit well. It gives you flexibility without starting from scratch.
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How Should a Bra Fit?
A well-fitting bra shouldn’t need your attention throughout the day. If you’re constantly adjusting it, something isn’t quite right.
The Band
The band should sit straight and level around your body and feel firm without being restrictive. If it’s creeping up your back, it’s usually too big and not offering enough support.
The Cups
Your breasts should sit comfortably inside the cups, with no spilling over the top or sides and no gaping or empty space. Both are signs that the size or shape isn’t quite right for you.
The Straps
Straps help with lift and shape, but they shouldn’t be doing all the work. They should sit comfortably on your shoulders without digging in or slipping down every five minutes.
The Centre Gore
The centre gore, the small panel between the cups, should sit flat against your chest. If it doesn’t, it can be a sign that the cups are too small or the style isn’t the best match for your shape.
Common Bra Fit Problems (And How to Fix Them)
If your bra doesn’t feel great, it’s usually trying to tell you something. A band that rides up at the back often means it’s too big. Cups that dig in or overflow suggest you need a larger cup size or a different style. Gaping cups can mean the cups are too big, or simply that the bra shape isn’t right for you. Straps that won’t stay put can point to a loose band, while underwire digging in usually means the cups are too small or the wire shape isn’t right for your body.
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Bra Styles Explained
Different bra styles suit different outfits, shapes, and moods. Knowing what they’re designed to do makes choosing much easier.
Balcony Bras
Balcony bras lift from underneath and create a flattering, open neckline. They work particularly well under square or wide neck tops.
Plunge Bras
Plunge bras are designed with a lower centre front, making them ideal for deeper necklines while still offering support.
Full Cup Bras
Full cup bras offer more coverage and support, making them a popular everyday option if comfort is high on your list.
Push-Up Bras
Push-up bras use padding or shaping to lift and enhance the bust, creating a fuller look when you want it.
Strapless Bras
Strapless bras rely on a secure band rather than straps, so getting the right size is especially important for comfort and confidence.
Sports Bras
Sports bras are built to reduce movement during exercise. They’re usually sized differently from everyday bras, so it’s worth checking the fit carefully.
The 2 Finger Rule for Bras
The 2 finger rule for bras is a quick and easy fit check. You should be able to fit two fingers comfortably under your band and straps. If you can’t, the bra may be too tight. If there’s loads of room, it’s probably not supportive enough. Like most fitting rules, it’s a guide rather than a strict rule, so always trust how it feels on your body.
When Should You Get Re-Measured?
Bra sizes aren’t set in stone. Weight changes, pregnancy, hormones, and natural body changes can all affect your fit. Bras also stretch over time, which means even your favourite styles won’t last forever. Re-measuring every six to twelve months can help keep things comfortable and supportive.
Bra Fitting FAQs
How do I know if my bra is the wrong size?
If it digs in, slips around, or needs constant adjusting, it’s probably not the right fit.
Should bras feel tight at first?
A new bra should feel firm around the band, but never uncomfortable or restrictive.
Why does my bra size change?
Your body changes over time, and your bra size can change along with it.
Can different brands fit differently?
Yes. Different brands use different shapes and materials, so fit can vary even in the same size.
Find Your Fit With Confidence
Finding the right bra isn’t about chasing a perfect number. It’s about understanding how bras should feel, knowing how to measure yourself, and trusting your comfort. Once you’ve got that down, finding a bra that fits well becomes far easier and a lot more enjoyable.