Why does my bathroom scale do this?

I have a cheap bathroom scale bought from Ikea. If I step on it in the bathroom I weigh 79 kg. But when my kids take it from the bathroom and put it on the bedroom carpet, my weight shows as 85 kg.

What gives? Where did the kilos come from/go to? And which is most likely correct?

  1. The carpeting is probably not supporting the bottom of the scale fully, so that the top and bottom platforms aren’t parallel when you step on it in the bedroom. This gives an inaccurate reading.

  2. Your bedroom is above the garage, where the mass of your car is attracting you enough to change your weight in the bedroom. :D:D

[nitpick]
You can’t weigh anything in kilograms, since it’s a unit of mass, not of weight.
[/nitpick]