Bra cup too big and too small at the same time: how is that possible?

Your cup isn't actually too big and too small at the same time: you're stuck between two sizes. That happens because cup sizes jump in whole letters (B, C, D), while your chest can fall somewhere gradually in between. Often your band size is a little off too, and that tilts the whole fit of the cup out of line. Below you'll find exactly which of these five things is going on for you, with a test you can do right now.

Why does one cup feel too small and the next too big?

Cup sizes go up in fixed steps: from B to C to D is roughly a 1-inch difference in volume each time. Your body doesn't grow in those neat jumps. If you land right between two of those steps, the smaller letter digs in and the bigger one sits loose. That's not a measuring mistake on your part, that's just how the system is built.

Try this test: close the bra on the loosest hook (that way you still have room later when the band stretches out). Bend forward from your hips, let your breasts fall all the way into the cups, and stand up straight. If you see a gap at the top of the cup where two fingers fit easily, that size is too loose. If you feel pressure on top of your chest, or something bulges out the side toward your armpit, it's too small. Feel a little of both? That confirms exactly the problem: you're stuck between two sizes.

Tight, couldn't find the right size. B too small, C too big. Band on the back that rides up. No problems with these bras. This is my 2nd order because I like them so much.

Out of nearly 2,900 women we asked about their biggest frustration, 8.2% name exactly this: the wrong size or cup. More than half of all complaints we get are physical, too, so digging in, pinching, cutting, not a looks issue. That makes this less about a perfect fit in front of the mirror and more about a bra that has to be wearable all day.

Our Daily Essential Bra uses memory foam cups that shape themselves to your chest instead of the other way around. If you're stuck right between two sizes, that gives you exactly the bit of give that a hard, fixed cup doesn't.

Your band is off, and that pulls the cup out of line too

You can't look at the cup size on its own: it's the difference between your bust measurement and your band size. If your band is too loose, the whole bra slips down a bit, and the cup suddenly feels too big because nothing stays in place anymore. If your band is too tight, it pushes your chest up into the cup, which then feels too small when the real problem is actually the band.

Try this test: push a finger against the band on your back. If you can fit more than two fingers under it, the band is too loose. In that case, order one band size smaller and one cup size bigger, because those two always trade off against each other: a 36C sits at roughly the same volume as a 38B. If the band cuts into your skin or you see a red line after a few hours, it's too tight, and you need the opposite.

We wrote more about this trade-off earlier in small band size, big cup: why does the underwire dig in then. If you feel like your cup size is right but it keeps gaping at the side, read bra cup too wide at the side: which size actually fits.

Your left and right breast aren't exactly the same

Almost nobody has two identical breasts. A difference of an inch or so between left and right is normal, but a bra gives both cups the same size. Pick based on your bigger breast and the other cup sits loose. Pick based on the average and the bigger one spills out.

Try this test: without a bra, measure your bust at the fullest point on each side separately with a tape measure. If you see a difference of more than one cup size, that's your answer for why one side never quite fits the same as the other.

The fix is usually simple: go with the size that fits your bigger cup. A cup that's a little loose on the smaller side is easier to live with than a cup that digs in on the bigger side.

Your breast shape doesn't match the shape of the cup

A cup letter tells you about volume, not shape. A breast that's wide and flat spreads that volume differently than one that's full and round. So two women with the same cup size can sit totally differently in the same bra: one spills out the side toward her armpit, the other has extra room up top.

Try this test: look at yourself from the side in the mirror with your bra on. Do you see flesh spilling out at the side near your armpit, while fabric hangs loose at the top of the cup? Then it's not the size that's wrong, it's the shape that doesn't match. Switching between the same two sizes again won't fix that.

Here, a cup that moves with your shape helps more than one that forces its own shape on you. That's why the Daily Essential Bra has a double shaping layer that holds everything together at the side, so your breast doesn't slip toward the side or your back, whether your shape runs wide or round.

Your body has changed, but the size on the label hasn't

After pregnancy, breastfeeding, a stretch of weight loss or weight gain, or just getting older, the shape and volume of your chest changes. Yet plenty of women keep buying the same size for years, simply because that's always been their size. That's exactly where the "cup too big or too small" complaint comes from: the bra hasn't changed, you have.

Try this test: if it's been more than 2 years since you last measured yourself, measure again now, even if you think you know your size. Especially after breastfeeding or a stretch of changing weight, there's a good chance your size has shifted.

Read more about this in bra for full breasts after breastfeeding twice: what to watch for and in bra fit off after weight changes: what now.

What you can actually do right now

• Measure again, even if you think you know your size: band measurement snug under the breasts, bust measurement at the fullest point.
• Stuck between two band sizes? Go with the smaller band and bigger cup of the two: 36D instead of 38C, for example.
• Still torn between two cup sizes? Go with the smaller band and bigger cup rather than the other way around: a loose band is harder to fix than a few extra millimeters in the cup.
• Use the included bra extender if your band is just a touch too tight, instead of ordering a whole size up right away, which makes your cup suddenly too loose.