How to take waist measurement, for BF calcs

[Taureanman]

Hi all - I am wondering how is the waist measurement to be taken properly?

I am interested in doing the waist minus wrist BF% calculation in Protein Power and I am not sure if waist is to be measured with belly relaxed (seems like you are just measuring the abdominal cavity) or sucked in (as per Dr. Mehmet Oz - since fat can not be compressed)?

(based on wrist measurement of 6.5")

Belly relaxed = 39" - = 25% BF!!! (trouble!)

Belly sucked in = 35" -> 18% BF - (within "Ideal Range")

Skinfold calipers at 4 points -> ~20% BF.

I know the mirror is the best indicator :-), but nevertheless I would like to zero in on my BF a bit for my records.

Thank you in advance!

[Spruce Goose]

I always take mine belly relaxed.

[Mitra]

I go for sort of normal muscle tone - not absolutely droopy, but not pulled in. A sort of good posture - not too tight, not too loose. It agrees more or less with my Tanita scales. I've only had a caliper measurement done once, and that came in at a slightly higher value.

I think the main thing is to be consistent from one measurement to the next.