I usually put a 5# bag of sugar or flour on to make sure its calibrated correctly. I kow I get upset when the dr's weigh me then I weigh myself at home. Seems like I always weigh much more there than I do on my own scale. I always think when you have 50 people of all weights on and off a scale in one day, it is possible to knock off kilter. I am using an old fashioned one rather a digital. I had the same problem with it always weighing one weight and I step off then on and I am 3 lbs heavier or lighter. It's frusterating.