Scales work on springs. Carpet is springy. When you put the scale on top of the carpet, and then stand on the scale, the carpet is absorbing some of the weight in its springiness, and the springs in the scale are compressing less.

Question:

I have just ordered a digital scale but the only hard flat surface in the house is in the downstairs hallway - I have carpet in the bathroom and my bedroom.

Now I don't really want to stand naked in my hallway so, is it good enough to put the scales on the carpet but stand it on, say, a piece of hardboard. Or would that not make any difference.

I have always weighed myself on analogue scales and found the results consistent if I always used the same surface each time (which happens to be carpet). The reasons I'm changing is because the display is very small and it's hard to tell if it's dropped a pound or not. I'm hoping a digital one will be clearer.

Had an idea - I tried weighing myself normally and then putting the scales INSIDE the shower cubicle which obviously has a hard floor and weighing myself again - it worked! It was about a pound and a half less.

So now I know where I can weigh myself with my new ones.