Not to Scale: One Size Doesn't Fit All?

According to a new investigation, your pants may not be the right size.

Sept. 10, 2010— -- Do those skinny jeans still fit?

Could your pants be lying to you?

According to a new investigation, they are -- and you might not want to hear the truth.

"Good Morning America" producer Bartley Price checked out four of America's most popular stores to see how pants sizes really measure up.

Price believes he has a 36-inch waist.

But after trying on some jeans, his true waist size seems to suggest he's even more slender than he thought.

"34 (inches) very tight…35 (inches) a little snug...36 (inches) a little loose," says Price.

GMA took four pairs of size 36 jeans to one of New York City's best tailors to find out if that 36 inch waist is really 36 inches.

This was the result of that test:

Levis: 36 and one half inches in the waist.

Zara's: 36 to 37 inches.

Gap: two full inches larger.

Banana Republic: 38 and a half inches.

"You know, it makes you think like you've worked so hard to lose weight and to be fit and they're telling you the wrong size," said Price.

Esquire Magazine, the first to investigate to so-called "vanity waistlines," found 36 inch Dockers were actually 39 and half inches round and Old Navy pants were a full five inches larger than the label.

"If a company says it's a 36, but it's actually 38, are men more likely to buy that jean? Yes, I've done it. I admit it," says Price.

But the companies say it's something else.

Banana Republic tells GMA their "pants are not specked to sit at the natural waist. They're specifically fit to sit lower on the high hip which is wider than the waist, therefore (our specs) may measure bigger than other pants..."

Gap says you can't compare sizing and "each retailer is designing for a different target customer."

Still, many men say they feel duped.

"I'm hurt. I'm hurt," Price said.