I've always had trouble getting consistent measurements of my waist because of how I hold myself. My 'natural' stance is sort of holding my stomach in, not all the way (I can still suck my tummy in further, but not actually hold in there for any extended period of time), but I actually have to concentrate to 'let my stomach relax' to push it out as far as it can go.

So my question is: when measuring to buy clothes online, should I measure at my 'natural' stance, or at 'as big as I can go'?

I do the same thing. For clothing, I would use the "natural stance" since that's how you are going to stand in the clothes anyways. I've been wondering about this because of health articles about waist to hip ratio... Also, is your "waist" at your belly button or what?

I agree, "natural stance" seems to make the most sense.

I generally assume my waist to be my narrowest part (which I hope to make narrower still! ) of my midsection. For me, that's an inch or two above my navel, but every body is a little different there.

The most important thing is consistency. If the tape winds up slipping to your natural thinnest part, that is your waist; if you've got a more athletic build or are an "apple" shape still working on finding your core, then go with a landmark like your navel or a beauty mark or something so you can get consistent measurements of the same area.

Where do you measure at the waist? I've been measuring at my belly button, but I keep thinking it's supposed to be right below the rib cage.

It's where the bend is when you bend sideways, mine is just below my ribcage and several inches about my belly button.

I read an article (a scientific article) which said there are several acceptable methods for measuring a waist. One was measuring the narrowest point, another was 1" above the belly button, I forget the other. The gist of the article was that it was bad to be above a certain waist size (which varied depending on BMI) but I was frustrated since it never weighed in on which place was best to measure (and for me there is a couple of inches difference depending on where measured). The article did say that to properly measure the waist the person being measured needs to exhale first.