Eighty percent of women are wearing the wrong bra size. Whether you're wearing a ratty old friend you're reluctant to replace, a fashion-y brassiere you like the color of or one in the size you've simply always worn, there's an overwhelming probability you're wearing an over-the-shoulder-boulder-holder that's wrong for you. "A lot of women stick to the number in their head from when they were first fit," Kay-Lin Richardson, director of sales and spokeswoman for Panache Lingerie explained. "They'll say, I'm a 34 B or a 36 C. I've been guilty of that. I couldn't imagine that I would ever be a D cup because that wasn't in my head and it wasn't my size." But what most women don't realize is that their bodies are constantly changing. A bra size could change with as little as a five-pound weight loss or gain, changing physical activity or even age. "You should probably get fit every year -- just go and check in to make sure you're still wearing the right size," Richardson told StyleList. "You probably are, but you probably wouldn't even realize that your bras aren't fitting anymore because that's just the way they've always fit you." It's a societal epidemic that women need to address. We're heavier than we've ever been, many women are augmenting their assets, and hormones in the food chain have changed the shape and size of assets. Consequently, there is a demand for sizes starting at 28 in band size and going up to FFF cups. The good news is that better data, improved engineering and manufacturers working with the changing bodies of women are creating choices where once there was none. "If you went online now and were a 30 FFF, you're not going to find the 34 B assortment, which is everything, but there's probably 100 styles for that customer," Richardson explained, which wasn't the case even five years ago. And that old rule of thumb about measuring your rib cage and adding five inches is pure malarkey. Each brand fits differently and a well-versed fitter will know what brands are true to that measurement and which ones you need to size up or down for. "Go to a store that has a good reputation for fitting women," Richardson said. Better specialty stores and a department store like Nordstrom usually have very good fitters. And if you have to shop online, follow the site's fit guide, but keep an open mind -- most of these sites have great return policies so you can try a couple of sizes and return what doesn't work. In case you're not sure if you're in the majority or minority, check you bra's fit against these guidelines: The band: Should be firm against your body to provide most of the support. The shoulder straps: Should not be taking the brunt of the weight. If they're digging into your flesh, you need a firmer fitting band. The underwire: Should encapsulate the breast and should tack firmly against the body. And sports bras are no different. They're usually sized XS to XL, and knowing your size gives you a good starting point. "Take several sizes into the fitting room," explained LeJean Lawson Ph.D., chief scientist at Champion, who helped invent the sports bra. "We don't come in specific sizes -- we're all on the continuum -- and the more atypical your body is, the more important it is to try different sizes." Lawson also stresses you need to take into consideration what you'll be using the sports bra for. "Not all sports bras work for all sports. You might need flexibility, do a lot of running, reach up like when playing basketball or if you're cycling, you might want more ease across the back. There are different design elements for each of these movements." There's one big misconception that's still out there, though, "Many women think of a sports bra as a compression, uni-boob thing," Lawson said, clarifying that there are sports bras that offer encapsulation, compression, spot comfort and more, but all deal with the most important performance needs: managing sweat, managing chafe and providing support without hardware that will hurt you. "At the end of the day, it's about being comfortable, looking and feeling good," Lawson concluded.