If you’ve ever walked out of a high street fitting room feeling like your body is the problem, you’re not alone. The truth is, most high street bra sizing is designed around a narrow range of bodies — and if you fall outside that range, the system fails you, not the other way around.
Here’s everything you need to know about finding your actual bra size — including why high street sizing doesn’t work for most people, and how to measure yourself properly at home.
Why High Street Bra Sizing Doesn’t Work
Most high street brands stock bras from around a 30A to a 40DD. That sounds like a reasonable range — until you realise that the majority of people who wear bras fall outside it. Large cup sizes, small back sizes, and anything above a G cup are routinely excluded from mainstream ranges entirely.
Even within the sizes that are stocked, fit is wildly inconsistent. A 36D in one brand is nothing like a 36D in another. Sizing conventions vary, vanity sizing is common, and the way a bra is constructed — the shape of the cup, the stretch of the band, the placement of the underwire — affects fit as much as the label does.
And then there’s breast shape. High street bras are typically designed for a “standard” breast shape that doesn’t reflect the enormous variety of real bodies. Pendular breasts, wide-set breasts, close-set breasts, full-on-bottom breasts — all of these require different construction, and most high street bras simply don’t account for them.
The Sister Size Myth
You may have been told to “sister size” — go up a back size and down a cup size, or vice versa, to find a better fit. While this can sometimes help, it’s a workaround for a broken system, not a solution. If the bra isn’t made for your body shape, changing the size won’t fix it.
How to Measure Yourself for a Bra
Measuring yourself at home is the most reliable way to find your starting size — especially when shopping from a brand that makes bras to their own patterns, like we do.
You’ll need a soft measuring tape. Measure in centimetres or inches — whichever you prefer.
Step 1: Measure your underbust. Wrap the tape measure firmly around your ribcage, directly under your bust. Keep it level and snug — this is your band measurement.
Step 2: Measure your overbust. Wrap the tape measure around the fullest part of your bust, keeping it level. Don’t pull it tight — let it sit naturally.
Step 3: Note both measurements. These two numbers are what you need to find your size using our Bra Size Calculator.
Watch Debz demonstrate exactly how to do this — including the real-life struggles that most measuring guides don’t show you:
Why Our Sizing Is Different
At Designed by Debz, our bras are made to our own unique patterns — not to standard high street sizing conventions. That means our sizes don’t map directly onto what you might be used to from M&S, Bravissimo, or anywhere else.
This is actually a good thing. It means our bras are designed around real measurements, not arbitrary conventions. But it does mean you need to measure yourself before ordering, rather than assuming your usual size will work.
We offer sizes from A to O cup and 3XS to 10XL — a range that goes far beyond anything available on the high street. If you’ve never been able to find a bra that fits, there’s a very good chance we have your size.
What If I’m Between Sizes?
If your measurements put you between two sizes, we generally recommend sizing up rather than down — a slightly larger bra that sits comfortably is almost always better than one that’s too tight. You can also get in touch with us directly and we’ll help you work out the best size for your measurements and body shape.
Find Your Size
Use our Bra Size Calculator to find your size based on your measurements, and check our full Size Guide for detailed measurements across all our styles.
Ready to find a bra that actually fits? Shop our handmade organic cotton bras and bralettes here.
