On the "Heat index," finding the perfect pair of jeans. We all know it's tough. And eight-in-one brand isn't the same as a size eight in another brand. It does eight things? A size eight in one brand... See More
On the "Heat index," finding the perfect pair of jeans. We all know it's tough. And eight-in-one brand isn't the same as a size eight in another brand. It does eight things? A size eight in one brand may not be the same in another brarndz. Becky worlworley, what did you find. When I find those eight-in-one jeans you'll be the first to get them. If you ever ordered online, you know how it is. You go et them in your side and when they arrive sometimes they fit. Sometimes they don't. Well why is that? That's the question we set out to ansz. ? 12 inches is a foot. 16 oupszs is a pound. So all size jeans should have the same measurements, right? Hmm. We ordered seven pairs of boot cut jeans all different brands. I normally wear a size. Size 8. We asked two teach attorneys try them on. These are super high waisted. Oh, yeah, I'm not buying these. Of the seven brands each Stever said only three fit them the way they expected. For Clair it was gap. J. Crew and express. For very lario, grab, J. Crew and Joe's and American eagle was the furthest from a good fight. I sit down and there's this. Reporter: We asked 9 instructors at San Francisco's academy of art university school of fashion to measure all the pants. All these size 8s were exactly the same size. Not exactly. Not even close. Reporter: They found the waist measurements rank from 31 inches all the way up to 35 inches. Probably wouldn't buy these. Reporter: Since some sat higher or lower. Too short in the back. Reporter: This is somewhat an issue of style, the hip measurement were just as wide ranking. Not too much give. American eagle the biggest at under 40 inches and Joe's were the narrowest at 36. So four inches of difference in the hips. That's quite a difference. Reporter: The leg circumference from a sizable span, two inches difference between the Joe's and Levi's. Is this range abnormal? Is there a stand forward for sizing. As far as I can see there is no standard. There's standards within a brand that conform form to what a customer wants. Reporter: Levi's responded saying trial is a critical component of finding the perfect fit. Joe's explained the measurement in leg opening is small story offer a sexier take on the traditional bootcut." Until we come up with virtual try-ons only way to find a good fit is one leg at a time. American -- we are and I have to start this by saying American eagle declined to comment for this story but our conversation is really why would they do this? Four inches of difference between these two size, it's a measuring employ. Once you know what size you are in a specific brand you have one brand you love? I do. I like ag. And then what's your fave? I like gap and I also like Joe's jeans. Once you're locked in, you're locked in for life because you know what size you are. It's all marketing, girls. Really. That is fascinating. Thank you very much, beck. Love that. And robin, you're outside.
This transcript has been automatically generated and may not be 100% accurate.