For many people, bra shopping falls somewhere on the emotional scale between flat-out disappointing and totally traumatic, and the same could be said for the actual wearing of said bras. Many women are wearing uncomfortable bras that dig into their skin, slip off their shoulders, and create awkward spillage situations—and then rip them off their bodies the minute they get home. A lot of this can be traced back to the lingerie store: If you don’t know how to find the right bra (or even the right bra size!), you’re not going to get one that’s best for you. Put simply, women aren’t getting the support they need to get the support they need.

To make sure you get the most out of this experience, I reached out to three stylists and bra fitting experts who gave a detailed rundown of tips you should consider when buying a bra. Their advice, from breaking down bra components to telltale signs when your bra is too small or too big, is useful for women of all ages and sizes. Read on for 11 things every bra-wearing person should know.

1. Most of the support comes from the band.

Cups hold the breasts in place, but the band is responsible for about 90 percent of the actual support (strapless bras exist for a reason). So while the straps may seem like they’re there to hold up your bust, they are really there to help keep your cup flush with your body and to shape your breast. In fact, if your band and cup both fit well, you should be able to slip off your straps and take a few steps while your bra stays in place, bra expert Kimmay Caldwell from Hurray Kimmay tells SELF.

2. You need to know your size and your “sister size.”

Just like with other notoriously difficult-to-shop-for items, like jeans, there’s a wide variation in how bras of the same size will fit from brand to brand, even from one style to another. That’s why experts say women should know both their true size and their sister sizes. If a bra doesn’t fit in your regular size, it might work in your sister size.

The rule of thumb is as follows: If you go up in the band, go down in the cup and vice versa. For example, a 32C could possibly fit a 30D or a 34B. If you’re a 34C, you might find bras that fit better in a 36B or a 32D.

Knowing your sister size is useful to accommodate for size differences between brands. It is also a good resource if your “real size” is hard to shop for. People with smaller bands and large cup sizes, or larger bands and smaller cup sizes, will benefit most from sister sizing.

3. There’s an equation for figuring out your band and cup size.

Your bra size is a ratio that combines the measurements of your cup (letters AA-M) and band size (numbered 28-44). It’s a really good idea for any woman to get a professional bra fitting at a boutique—you might be surprised what a bra expert will tell you, such as you’ve been wearing the wrong size your whole adult life. You can also measure yourself at home with some tape.

To measure at home, you’ll need two measurements: around your back and under your bust for your band size, and around your back over your nipples for your cup size. You’ll then subtract the difference. For example, if your bust measures 35 inches and your under-bust (or rib cage) 32 inches, you’ll be a 32C because 35 minus 32 equals 3, and that number corresponds to the letter “C” in the alphabet.

4. If your breasts are two different sizes, round up.

It’s totally normal and really common to have one breast that is bigger than the other. If the difference is significant enough that it makes bra shopping even more complicated than it already is, Cora Harrington, lingerie expert and author of the upcoming book In Intimate Detail: How to Choose, Wear, and Love Lingerie, suggests fitting to the larger breast. If you want, you can even out the appearance by adding a bra cutlet to the smaller breast, or getting a bra with removable pads and taking them out on the big side.

5. If bras straps are digging into your shoulders, it could mean your cups are too small...

If your breasts are spilling out around the edges of the cup, they might be putting a lot of extra weight on the straps—and you may find yourself pulling the straps taut to hold them in check. Either way, your shoulders would probably benefit from larger cups.

6. ...or your band is too big.

Your straps could also be digging into your shoulders if your band is too loose, making it so your straps are doing all the work. Take a look behind you in the mirror: If your straps are pulled so tight that they're yanking your strap up, it's probably too big or is too stretched out to do its job.

7. If your straps are slipping, it could be one of a few signs that your cups are too big.

Another tell is if the center gore, or the center panel on the front your bra between the cups, is floating away. It should lay flat against the middle of your chest. And obviously, if the cups are gapping because your breasts are not filling them all the way, you may want to go down a cup size.

8. The band should be snug, not suffocating or loose.

When you’ve got the right band size, you should be able to fit your finger between your back and the strap with only about an inch of stretch. Your band is too small if the underwire is squeezing or digging in your breast tissue. But looser is not better when it comes to support. Caldwell notes that most people think loose means more comfort (think: caftans or sweatpants), but that doesn’t work for bras. Remember that the band is what accomplishes most of the holding-up of the breasts, so a loose band that rides up between your shoulder blades will not provide the support you need and leave you less comfortable in the long run.