How to Accurately Measure Waist

sewedo1

I thought I knew how to measure; however, when I looked at various weight loss calculators online and then at several sites describing how to measure, I'm a little confused. Some instruct to measure at the narrowest point "halfway between the belly button and rib cage" and others says "place the tape measure just above the belly button". One measurement gives me 34 and the other 36 so that makes a difference when trying to use the fat %age calculators (and I do realize these are only rough estimates).