If you have something around your house with a pre-determined weight (hand weights, bag of potatoes, cat litter-because I always have that
), set those on both scales, see if they are both weighing accurately. If one's off, obviously don't use that one, if they both come out the same, pick the one that works all the time, then don't pay attention to other scales. I have a super cheap analog scale, if my eyes aren't completely awake in the morning, I get a general estimate of my weight. It is the only scale I ever use. Even if I'm at my parents for a few days and the need to weigh myself is driving me crazy, I will still just wait until I get home. I have enough to stress over, fluctuating scale measurements is not something I want to add to the list.