When you measure your bicep, chest, waist, etc and report them here, do you measure flexed or relaxed? What is your reasoning behind this?

I've been measuring relaxed because that is how mybodycomp.com needs it for body fat estimation, but flexed I'm obviously bigger. So, which one is correct, or should be correct?

... when there's a reason to do it one way or the other.

So, for mybodycomp.com, you want to follow their rules. But for posting how big your arms are, you'll probably want to use flexed.

It's the same thing with measuring your "waist". Sometimes, this is the narrowest portion of your torso (mybodycomp.com), other times (like when you're computing body fat by wrist and waist alone), "waist" is the widest portion of your torso, usually at your bellow button. When I'm buying pants, I think of my waist as my beltline, which is usually at the top of my hips.

None is right or wrong ... just appropriate for the circumstances.

This does help point up the need to define your terms up front whenever you're discussing many of these measurements.