Vanity sizes causing fitting room frustrations

(CBS News) -- When it comes to shopping for clothes, many Americans don't know what size they are.

Courtesy: CBS News

There is no standardized sizing, which has led to fitting room nightmares and billions of dollars in returned clothing.

Your clothing size may be a better measure of your mind, than your waistline.

The question, "What size are you?" can be accompanied by a complex answer.

"So if I go to H&M, for instance, I will grab anywhere from a four to and eight. Now, if I went into J.Crew, I could wear anything from a double zero to a two," said Christine Cameron, a fashion blogger.

This fitting room frustration comes from "vanity sizing" - clothing brands put smaller numbers on tags while Americans get bigger. Fashion Institute of Technology professor, Shawn Carter, says it's all a mind game.

"Vanity sizing is a way for luxury brands and other brands in fashion to help a customer feel good about themselves by saying 'You're a size 2,' but when you look at their measurements of bust, waist and hip, they could be a size 6 or even a size 8," said Carter.

A size eight today would have been considered a size 14 in 1958.

Giving larger clothes smaller numbers has forced manufacturers to create new sizes, like zero and even double zero.

One way to know your true fit is to measure your bust, waist and hips. Most retailers provider fit charts online - so you can translate your measurements to their sizes.