Clothing sizes are all over the place. Across different brands—and sometimes even within the same one—your size can fluctuate a range of numbers. And if it seems like over time your go-to size feels roomy while you aren't actually losing weight, you're not going crazy. That's vanity sizing.

A recent story in The Washington Post highlighted the rise of vanity sizing with a graphic illustration. Here's how they break it down: "A size 8 dress today is nearly the equivalent of a size 16 dress in 1958. And a size 8 dress in 1958 doesn't even have a modern-day equivalent—the waist and bust measurements of a Mad Men-era 8 come in smaller than today's size 00." The data comes from the American Society of Testing and Materials and is pretty eye-opening.

No woman can be defined by just a number, and while vanity sizing is intended to flatter shoppers, in truth it can make finding clothes that fit just plain complicated. Take a look at this graph for yourself.

If you're wondering which brands are offenders of vanity sizing, check out this graphic from FitBay.