I think bra buying can be as difficult as finding a new pair of jeans that fit perfectly. 81% of women are said to be wearing the wrong size bra, but many still don’t know how to measure properly. They’ll just continue wearing the size they’ve always had until they get so uncomfortable, or discover a better way to measure.

I was probably a late developer (certainly compared to nowadays), living in crop tops until probably the end of secondary school before switching to bras. I think my mum measured me, using the method she’d always used. Take the band size, then if it’s odd inches add 5, or even add 4. Measure the bust size and compare the 2 measurements to work out the cup size. Otherwise I’d had the same measurement at an independent bra shop when I bought a strapless bra for under my wedding dress.

I was wearing a 34A right up to mid pregnancy. By post pregnancy I’d gained a band size thanks to an expanding ribcage. Over the years with weight gain I’d used the same measurement method and ended up a 38B-C. I lived in t shirt bras, mostly from Marks & Spencer, although balcony ones post pregnancy were getting harder to find because everything seemed to be full cups.

When lockdown happened and working from home, like many others I pretty much gave up wearing bras. Then things started opening up and I moved to non wired/bralette styles that were more covered but still comfortable, mainly because my wired bras just didn’t fit.

But after losing weight, I needed new bras. My old ones still didn’t fit – gaping cups, and the style didn’t suit. I searched online for a measurement calculator. I’d assumed I’d just be going back down to a 34 band, but couldn’t work out the cup sizing. With my 38Cs gaping badly in the cup, I assumed I’d need to go down a cupsize too.

bust sizes and bra buying solved

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Bra measurements

Then I discovered BOB.

The Boob or Bust method and its Boob or Bust calculator.

In my opinion (and thousands of other women), the doyenne of bra sizing and information about boobs.

Much to my astonishment, my sizing was totally different. I was spot on with the 34, but an E cup. Given I’d always thought myself as being pear shaped with not a lot up top, I was surprised. But sometimes you have to give into the process and trust the calculator is right. After all, if there’s an online bra measuring calculator that will give you the right starting or end measurement, then there’s no need to go into a store.

I’m not the only one surprised. Given the main high street shop people buy bras from (M&S I’m talking to you, along with many others) measures using an old method of adding 4 to your rib measurement to get the band size, women end up with much smaller cup sizes to make them fit, I’m amazing more people aren’t realising their bras don’t fit properly. So many people use boob or bust to find their size, and then question the results because they can’t believe their size is really so different.

How can I be that size, I’m small.

My current bra gapes, so how can I be a smaller cup size measurement.

I won’t be able to get into a smaller band size.

Most people I hear of, drop 2 band sizes, but go up usually at least 2 cup sizes.

The calculator is only a starting guide but works for the majority of people who end up extolling the virtues of the BOB calculator.

The BOB sizes tend to increase the cup size vs the band size that often goes down – their more accurate cup sizes go against what we’ve been told over the decades. That C cup is average and anything over D is huge. When really it’s not at all.

How does the boob or bust calculator work?

You just follow the guidance for how to measure, and input your dress size and 4 measurements. Under bust measurements – both at tight as a tape measure will go, a snug measurement, then a standing overbust measurement and one while leaning over.

Then the calculator spits out the size.

Boob measuring – bra guidance and resources

The Boob or Bust website has a huge number of resources along with diagrams that make you go ‘ah yes’ and makes everything make sense.

The shape – which way do yours point when leaning over – which guides you on which style bras fit best.

How to check bra fit by doing a back to front band test.

How to put a bra on properly by scooping and swooping. (It amazes me how many women don’t know about this).

The different in cup sizes vs band sizes, and how you can use sister or relative sizes.

Who knew how complex bras and measurements were? I didn’t. But now I’ve spent so much time working out the best bras for me, I’m a bit obsessed. It seems all these years, we’ve been told that anything over a C cup is huge with not many high street stores offering sizes over D or E cups. But since joining the Boob or Bust community I can’t recall anyone saying their BOB measurement is a C or under. Even teens looking for first bras are easily measuring D+ sizes. And many people are surprised to find themselves actually under 32 inch bands.

red bra on show by person in store

Finding a new bra

I never thought finding a new bra that fits would be so hard. My recommended bra shape is balconette or plunge. With balconettes I find they cut me across and aren’t that flattering. With balconies I find they can fit ok if they have elasticated lace on the top part. Plunge look ok but I find they come up so high on the straps, they show above my vest tops. Fine in winter, but not good with thinner or more skin showing tops in summer.

It seems M&S bras no longer fit. Either the ones I like aren’t in the cup size I need, or the style isn’t suitable. Since getting my new BOB size, I think I’ve probably tried on about 50 bras, and bought 7 or 8 of varying styles and colours to work under different tops.

Most I’ve bought online – luckily there have been some good sales – and also went to Bravissimo. Pre this measurement I’d never have thought their bras would fit given they start at DD cup. If you want a fitting they do contact free / by sight measuring, then work with you on different bras and sizes, checking the fit for you as needed. I already had my measurement, but I ended up going down a band size, and up 2 cup sizes in the bra style I liked.

Now I’m confident in knowing what a well fitted bra looks and feels like for me, I could check out cheaper bras from high street stores. But there aren’t many that go past a D cup. Primark stop at a D unless you’re lucky with the style you’re looking for. M&S, in the bras I like, stop at D or E. I did find 1 nice bra that fit in Asda. Sainsbury’s choice of bras is pretty limited. So it’s going to be a case of checking out sales and using cashback to buy online.

Buying online isn’t great for bra shopping because a lot of bras end up not fitting and being sent back. Luckily the good bra specialist retailers tend to have decent length return policies to allow for getting fit checks.

Bra buying can be a long process. You need to have faith in the BOB calculator as your suggested starting size, then can play with it depending on the brand and style you’re trying.

Tips for bra buying

  • Use the BOB calculator. It’s a more accurate calculated size using your true band size.
  • Cup size is relative to band size. The volume of the bra is the same for a 34E as for a 36DD and a 32 F.
  • Remember over a D cup isn’t large. You can find the Irish Bra Lady on instagram to compare sizes and realise that average isn’t really a 34C.
  • You’ll need to try on lots of bras – and to check the fit, the band test is the first step,
  • The bra should be worn right up into the breast crease and you need to scoop and swoop to get all of your breast tissue into the cups.
  • You should start wearing a bra (assuming you’re not under 18 or pregnant) on the loosest hook. Over time this means you’ve got more wear to tighten the hooks.
  • Ideally handwash bras, or if not (like me), wash them on a gentle wash, putting them in a mesh bag to wash.
  • Moulded bras are a lot harder to fit as you need to have exactly the right shape breasts to fit the moulded shape.
  • Darker bras sometimes fit smaller than lighter coloured bras in the same size due to the dyes used.
  • Not all brands of bras include all the cup sizes, they skip sizes (especially high street stores like M&S or supermarkets). So if you’re a larger cup size, make sure you count up the cup sizes so you get the correct cup rather than your usual letter.
  • There’s so much terminology if you struggle to find bras that fit properly. What with gore, projection, east – west, roots and more. If you struggle to find suitable bras, there’s more you can check before finding the most suitable brands for you.
lady holding black bra up in front of h

There’s lots of other tips and advice on the boob or bust website, as well as a Facebook community you can join. There you can get bra recommendations that other people wearing your size swear by.

I’m just amazed at how much there is to think about when buying a bra. To getting a good fit that looks good under clothes and is comfortable to wear all day. I thought I’d not go back to wearing wired bras, but a good fitting wired bra is so much comfortable than non wired ones.

I’ve got so into my bra buying over the last 2-3 months, I can’t stop telling everyone about the calculator and how accurate it is.

Bra retailers I like:

  • Brastop – online, DD+, offers a range of brands, good sales
  • Bravissimo – online and high street. No contact fittings, also has bra size swimwear
  • Boux Avenue – up to G cups, good for smaller band sizes, also swimwear
  • Belle Lingerie – good promotions, range of brands, returns only 28 days
  • Lingerie outlet store – good discounts, free returns via Asda only.

Have you ever used the boob or bust calculator? Did you find a massive change in size? What bra buying issues do you find?

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