The measurements aren't always that accurate if you have an abnormal body type or shape -- really short/long waisted, very muscular, unusually tall or short, etc. Sometimes you kind of have to pick the right method for you based on intuition about your body type and general toned-ness. MyBodyComp puts my LBM ~8.5 lbs lower, and my body fat 7.5% higher, than the handheld measurement gadget at the gym; but based on my general proportions, I think the lower body % is probably the right one.