How to Measure Bra Size
Most women who come to us for a fitting have been wearing the wrong size for years — usually a back that's too big and a cup that's too small. It's one of the most common things we see, and it makes an enormous difference once it's corrected: not just in terms of comfort, but in how your clothes look and how you carry yourself. Getting a bra that genuinely fits is one of the simplest things you can do for your silhouette.
At Caroline Randell we don't use a tape measure. In our experience, measurements alone can't account for breast shape, projection, or how a specific style sits on a particular body — and these things matter just as much as numbers. Instead, we assess each customer individually, using our fitting expertise and detailed knowledge of how our brands and styles work across different shapes and sizes.
If you'd like a fitting, there are two ways to do it. You're very welcome to visit us at our Wimbledon Village boutique, where we offer one-to-one fitting appointments Monday to Saturday. Alternatively, we offer virtual fittings via WhatsApp — and these work remarkably well. We'll have a conversation about how you feel in your current bras, what you're looking to achieve, and the styles and occasions you're dressing for. We then ask if you're comfortable sharing a photo of the front and back of the bra you're wearing now. Based on that, and drawing on years of fitting experience, we can give you an accurate size recommendation across our brands — bearing in mind that you won't be the same size in every brand, as they're cut differently. Our clients tell us how well this works. To arrange a WhatsApp fitting, get in touch here or call us on 020 8946 6171.
Six Signs Your Bra Fits
Whether you're trying on a new bra at home or checking the fit of one you already own, these are the six things to look for. A well-fitting bra should pass all six.
1. The band lies flat against your body
The band should sit horizontally and parallel all the way around — level at the front and back when you look at yourself side-on in the mirror. It should feel firm but not tight, and you should be able to slide two fingers underneath it but no more. If the back is riding up towards your shoulder blades, the band is too big: try a size down. As a guide, if you drop a back size, go up a cup size to maintain the same cup volume (a 34D and a 32E, for example, hold the same cup size).
2. The underwire follows your breast root
The underwire should curve snugly around the entire base of your breast, sitting flush against your ribcage. It should never dig into breast tissue at the sides, sit on top of the breast, or lift away from the body. If the wire is cutting into you or sitting on the breast rather than beneath it, the cup is too small — try going up a cup size.
3. The centre gore sits flat against your chest
The piece of fabric between the cups — the centre gore — should lie completely flat against your sternum. If it's pulling away from the body, this usually means the cups are too small and your breast tissue is pushing it forward. Try a larger cup size. If it sits away because the bra simply doesn't suit your shape (some people have breasts that sit further apart), a different style may be the answer — this is something we can advise on.
4. The cups lie smooth with no spillage
Your breast tissue should be fully contained within the cup, with no spillage at the top, sides, or underarm. To make sure everything is properly seated, lean forward slightly and use your hand to gently scoop any breast tissue from the sides into the cup — this ensures the underwire is sitting correctly at the breast root. If the cup fabric wrinkles or gaps, the cup may be too large; if there's a double-bust effect at the top, it's too small.
5. The straps sit comfortably on your shoulders
Straps should rest lightly on the shoulders — enough to keep the cups in place, but not doing the heavy lifting. Most of the support (around 80%) should come from the band, not the straps. You should be able to slide two fingers comfortably under the strap. If your straps are digging in or leaving marks, the band may be too loose and you're relying on the straps to compensate. If straps slip off the shoulder, try adjusting them first; if that doesn't help, a different strap placement or style may suit your shape better.
6. It's comfortable
This sounds obvious, but it's worth saying: a well-fitting bra should be comfortable all day. Not something you can't wait to take off. If you're adjusting it, pulling it down at the front, or conscious of it throughout the day, something isn't right — and it's almost always a fit issue rather than a comfort issue with the bra itself. Always fasten a new bra on the loosest hook; as the elastic relaxes with wear and washing, move to a tighter hook to maintain the fit.
Sister Sizing — What It Means
Cup size is relative to back size, not fixed. This means that as you change back size, the cup volume changes with it — so a 32E and a 34D hold exactly the same cup volume, just on different band widths. Going down a back size and up a cup size (or vice versa) keeps the cup volume the same. This is called sister sizing, and it's useful to know when a bra fits perfectly in the cup but feels slightly too loose or tight in the band.
As a guide: 30F = 32E = 34D = 36C = 38B are all the same cup volume on different band sizes.
How Often Should You Be Fitted?
We recommend a fitting every six months, or whenever your body changes — weight fluctuation, pregnancy, breastfeeding, surgery, and even changes in exercise habits can all affect your bra size. Many of our clients are surprised to find they've been wearing the wrong size for years, often because a size they were fitted into a decade ago has simply stuck. If your bra no longer feels right, trust that instinct and come in.
To book an in-boutique fitting or arrange a WhatsApp fitting, visit us at 6 Church Road, Wimbledon Village, London SW19 5DL, call 020 8946 6171, or get in touch online. We're open Monday to Saturday, 10am–6pm.
You can also browse our full lingerie collection, including brands we fit most regularly: Empreinte, Marie Jo, Aubade, Simone Pérèle, and Prima Donna.