Before we get into the different methods of sizing, let's first talk about how bra sizing works. Bra sizes are actually two sizes combined into one—a band size and a cup size—which can be found with two simple measurements: your band and your bust. Your band measurement is taken around your ribcage, just below your bust, and your bust measurement is taken around the fullest part of your breasts. The difference between these two numbers gives you your cup size and voila you have your bra size! Easy, right?

Unfortunately, getting the perfect fit usually takes a little more work than that. The best way to get the right size is with a professional bra fitting at a specialty lingerie store, but if that's not possible you can visit our Size Guide and Fitting Tips pages for detailed instructions on finding the perfect fit.

You may be surprised to find out that 80-90% of the support a bra gives comes from the band. A well fitting band should be parallel to the ground and be snug but not tight—you should only be able to fit two fingers between your back and band, and the gore (the center of your bra) should sit flat against your sternum.

If you've been wearing a band that's too big, you're probably always tightening your straps but never getting enough lift, and you can probably feel the underwires rubbing against you all day. The right band size can fix all of that! The first time you put your correct size on it may feel a little uncomfortable, but give it a try and you'll be amazed at how good your back feels and how much better your clothes look!

So now that we know how important band size is, let's talk about band sizing methods. First up is the method we use when fitting our customers: plus 0 sizing.

Plus 0 sizing simply means that when you take your underbust measurement, you round to the nearest even number and add 0 to get your band size. For example, if you measure a 33" underbust, you round up to 34 and that's your band. In most cases, this using this method to get your bra size will make sure your getting the best support in the most comfortable way.

Plus 0 sizing is most commonly found among UK brands such as Elomi and Panache, which is one of many reasons we love them here at Hourglass Lingerie.

Plus 4 sizing is where things start to get confusing. The "plus 4" method involves taking your underbust measurement, rounding to the closest even number, and then adding 4 to get the band size. So with this method, if you measure a 33" underbust, you round to 34 and then add 4 to get a 38 band. The result of this method is that more than likely you end up with a band that's way too big (not always, but we'll get to that in a bit).

At first glance, plus 4 sizing seems to make no sense. If your band is supposed to be snug, why would you need 4 extra inches? To get our answer we have to go back about 100 years.

The plus 4 sizing system comes from the pre-1950s era of stiff bras. When bras were mostly made of woven silk and cotton, the extra inches were necessary to allow women to move and breathe comfortably. Nowadays, most bras are made using PowerMesh—a super supportive and stretchy fabric that can move with you while remaining snug enough to still be supportive—which means we no longer need those extra inches.

I said earlier that plus 4 sizing doesn't always give you the wrong band size, and now I'll explain why. Sometimes brands will take plus 4 sizing into account while making their bras and will make the band 4 inches smaller than the labeled size. So a labeled 38 band bra will actually fit someone with a 34" underbust properly.

This kind of labeling is very common among European brands whose bands are originally sized by centimeters and then converted to inches using the plus 4 method for US markets. Luckily, European brands will almost always have both band sizes listed on their labels and size charts. For example, a European bra tag might have both a 75 and a 34 listed as the band size. 75 cm = 29.5 in so that bra will fit someone with a 30" band, but using the plus 4 method it's labeled a 34. When buying European bras, always go by the centimeter band size, otherwise you'll end up with a bra that's way too tight.

If plus 4 sizing wasn't confusing enough for you, it's about to get worse. The biggest problem is that oftentimes brands don't tell you what sizing method they use. This is especially common with US brands who often use the plus 0 method while making their bras and then the plus 4 method when making their size charts. So a 34 band = 34" underbust, but their size chart tells you to get a 38 instead. Inaccurate size charts with outdated sizing methods are one of the main reasons up to 80% of women are wearing the wrong bra size and why so many of us dread bra shopping.

This is why we always recommend buying bras in-person at a local, specialty boutique—rather than a chain or department store—with an experienced bra fitter so you don't have to worry about charts and labels. If you have to order online, make sure they have a good return policy or buy from a brand you know fits you well.

Plus 4 sizing is a headache for sure, but lets go over some other reasons you may have a few different sizes in your bra drawer.

Whether a bra is made using a stiff silk, stretchy cotton knit, or super-strong Powermesh greatly affects how a bra fits and feels. Even the dye used can make the same bra fit differently in another color—black dye tends to shrink fabric. If you have a bra that's super comfortable and fits amazing, take a look at the care tag and look for bras with a similar composition.

The style and purpose of a bra can change what size you need and how it fits. Strapless bras tend to be tighter because the band has to provide 100% of the support with no assistance from straps. The same goes for sports bras which have to work much harder than your everyday bra. Bralettes on the otherhand are meant to comfortable so they usually have a slightly bigger band.

This point also works with cup sizes. With an extreme plunge, you may have to size up in the cups to avoid spilling out, while with a full coverage you might size down to avoid wrinkling in the cups.

You've probably heard of vanity sizing when it comes to clothes, but it also affects the world of bras. If you don't know what vanity sizing is, it's when a brand keeps the measurements of a garment the same but changes the label to a lower letter/number. The idea is that if a brand tells you you're a smaller size then you're more likely to shop there again. The result is that nobody knows what size they actually are.